Learn With Reshu

2022-12-14T01:37:00.001-08:00

Running and Building Gradle with Different JDKs - Sip of Java

If you are using Gradle as the build tool for your projects and want to work with the latest JDK releases or early-access builds, you might think you are stuck until Gradle supports those versions of the JDK, which might take a few months. However, that’s not the case, and we will explore in this article how to run Gradle with one JDK version while building and testing with a different JDK version.

Managing Multiple JDKs

When working with multiple JDKs, using a tool like SDKMan or Jenv (for macOS) is highly recommended. These tools enable you to easily manage and switch between your local JDKs. This article assumes that you have multiple JDKs installed on your system: one for running Gradle, and the other for executing the tasks in the build. Be sure that the JDK installed to run Gradle is supported by Gradle. As of the time of this article, the latest Gradle version is 7.6 which supports JDK 19.

Configuring the Toolchain

By default, Gradle will use the JDK that is being used to run Gradle itself to execute the tasks in the build. This can be easily changed by configuring your toolchain. In the example below, Gradle will use JDK 20 to execute the tasks in the build regardless of the JDK version being used to run Gradle.

java {
    toolchain {
        languageVersion.set(JavaLanguageVersion.of(20))
    }
}

There are a few default behaviors Gradle uses to find a JDK install. Depending on your OS and if you have a JDK manager installed, Gradle will check certain places on your system to see if it can find the requested JDK version. If it is unable to find the requested JDK version, Gradle will attempt to download the requested JDK version. Be sure to check the Toolchains link under the Additional Reading section which provides the full explanation of this lookup process.

Setting JDK Version with Properties

Gradle’s default behavior for looking up a JDK version can be disabled through properties if it doesn’t match your needs. This can be helpful if you are working with multiple JDKs of the same version or running builds on a shared system.

To disable the auto-detection of a JDK, set the org.gradle.java.installations.auto-detect property to false like below:

org.gradle.java.installations.auto-detect=false

To disable the auto-downloading of a JDK, set the org.gradle.java.installations.auto-download property to false like below:

org.gradle.java.installations.auto-download=false

Finally, you can configure Gradle to look in a specific location for a JDK by providing it with an environment property, like in this example below:

org.gradle.java.installations.fromEnv=JAVA20_HOME

Spring Core

2022-12-01T13:34:00.001-08:00

The “Spring Framework” is a large project. Under the Spring Framework label are actually about 20 different Spring projects. Spring MVC, Spring Security, Spring Integration, etc. So, it would be easy to get confused about what “Spring Core” is.

The official Spring documentation, contains this image:

“Spring Core” is typically used to refer to the functionality of the Core container. Beans, Core, Context, and SpEL.

While there are about 30 Spring Framework projects, they all depend on this core container. Its this core functionality that has been around since the beginning of the Spring Framework. The core container, which has the Spring Context, manages dependency injection for us via Inversion of Control is used by all other Spring projects.

Spring Boot Application In Hindi

Cheers,

Learn with Reshu

Web Browsing || How does It works?

2021-06-30T14:37:00.008-07:00

Web Browsing and How it Works?

A web browser (commonly referred to as a browser) is application software for accessing the World Wide Web. When a user requests a web page from a particular website, the web browser retrieves the necessary content from a web server and then displays the page on the user's device.

A web browser is not the same thing as a search engine, though the two are often confused. A search engine is a website that provides links to other websites. However, to connect to a website's server and display its web pages, a user must have a web browser installed.

How Web Browsing Works?

How does a web browser work? A web browser takes you anywhere on the internet. It retrieves information from other parts of the web and displays it on your desktop or mobile device. The information is transferred using the Hypertext Transfer Protocol, which defines how text, images and video are transmitted on the web.

Suppose,

You need to request a google search engine page so what you will going to write on the URL will be https://www.google.com.

So you will get the Google search engine page directly. But Do you have any idea

What's the process behind that?

I real world this how its work

First our Request goes to ISP(Internet Service Provider), ISP then transfer our request to DNS.

And Now question is what is DNS?

DNS Is a kind of Library which holds number of IP Addresses and return the IP Address of the particular URL which has been questioned to it.

In this case its https://www.google.com.

Then the request with some IP Address comes back to ISP and the ISP send the response to our client machine.

But hold on, How its shown as a google search page.

It has a separate story behind it.

In the picture above the response returning with three files HTML CSS and JavaScript

Yes that's the answer.

We got response in the form of a web page which has built with a base made by HTML some beautiful page designs made by CSS and the functionality made by JavaScript.

Yes there are some other files to like images videos or some documents we get too. but that depends Totally on which request we a performing.

So as In the above picture we can see. that Google server has sent a response to the client machine in the form of Html CSS and Java script.

And then we got what?

We got our response as Google search page

So This is how Web browsing Works Hope you have enjoy the Blog. And If yes Please leave a nice comment for the motivation....

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Abstraction in Java, How Abstraction works in java with example code

2020-10-29T02:59:00.007-07:00

Abstraction in Java, How Abstraction works in java with example

Class
Objects & Methods
Inheritance(IS-A)
HAS-A Relationship Association

Aggregation
Composition
Polymorphism
Method Overloading
Method Overriding
Abstraction in Java (Security)

Abstraction
Data Hiding
Encapsulation
Tightly coupled Classes

What is Abstraction
abstraction is a process of hiding the implementation details from the user, only the functionality will be provided to the user. In other words, the user will have the information on what the object does instead of how it does it.

How to achieve Abstraction

Abstract Class (0-100 %)
Interfaces (100 %)

let's consider a Car, which abstracts the internal details and exposes to the driver only those details that are relevant to the interaction of the driver with the Car.

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Interface in Java

2020-10-29T02:31:00.006-07:00

Interface in Java

What is Interfaces

Another way to achieve abstraction in Java, is with interfaces. It’s a blueprint of a class, which tells by class what to do not how to do.

An interface is a completely "abstract class" that is used to group related methods with empty bodies.

Features of Interfaces

It is used to achieve abstraction.

It supports multiple inheritance.

It can be used to achieve loose coupling

Like abstract classes, interfaces cannot be used to create objects

Interface methods do not have a body - the body is provided by the "implement" class

On implementation of an interface, you must override all of its methods

Interface methods are by default abstract and public

Interface attributes are by default public, static and final

An interface cannot contain a constructor (as it cannot be used to create objects)

Why and When to use Interfaces

1) To achieve security - hide certain details and only show the important details of an object (interface).

2) Java does not support "multiple inheritance" (a class can only inherit from one superclass). However, it can be achieved with interfaces, because the class can implement multiple interfaces. Note: To implement multiple interfaces, separate them with a comma.

Ex. Class A implements B, C, D{

}

Java Interface Example

In this example, the Printable interface has only one method, and its implementation is provided in the A6 class.

interface printable{
void print();
}
class A6 implements printable{
public void print(){System.out.println("Hello");}
public static void main(String args[]){
A6 obj = new A6();
obj.print();
}
}

Output:

Hello

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Loops in java With Example Code

2020-10-29T02:21:00.002-07:00

LOOPS IN JAVA WITH EXAMPLE CODE

In programming languages, loops are used to execute a set of instructions/functions repeatedly when some conditions become true. There are three types of loops in Java.

for loop
while loop
do-while loop

Java For Loop vs While Loop vs Do While Loop

Java For Loop

The Java for loop is used to iterate a part of the program several times. If the number of iteration is fixed, it is recommended to use for loop.

There are three types of for loops in java.

Simple For Loop
For-each or Enhanced For Loop
Labeled For Loop

Example:

01. Simple For Loop

//Java Program to demonstrate the example of for loop
//which prints table of 1
public class ForExample {
public static void main(String[] args) {
//Code of Java for loop
for (int i=1;i<=10;i++){
System.out.println(i);
}
}
}

Output:

02. For-each or Enhanced For Loop

//Java For-each loop example which prints the
//elements of the array
public class ForEachExample {
public static void main(String[] args) {
//Declaring an array
int arr[]={12,23,44,56,78};
//Printing array using for-each loop
for(int i:arr){
System.out.println(i);
}
}
}

Output:

03. Labeled For Loop

//A Java program to demonstrate the use of labeled for loop
public class LabeledForExample {
public static void main(String[] args) {
//Using Label for outer and for loop
aa:
for(int i=1;i<=3;i++){
bb:
for(int j=1;j<=3;j++){
if(i==2&&j==2){
break aa;
}
System.out.println(i+" "+j);
}
}
}
}

Output:

Java While Loop

The Java while loop is used to iterate a part of the program several times. If the number of iteration is not fixed, it is recommended to use while loop.

public class WhileExample {
public static void main(String[] args) {
int i=1;
while(i<=10){
System.out.println(i);
i++;
}
}
}

Output:

Java do-while Loop

The Java do-while loop is used to iterate a part of the program several times. If the number of iteration is not fixed and you must have to execute the loop at least once, it is recommended to use do-while loop.

The Java do-while loop is executed at least once because condition is checked after loop body.

public class DoWhileExample {
public static void main(String[] args) {
int i=1;
do{
System.out.println(i);
i++;
}while(i<=10);
}
}

Output:

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Exception Handling in Java

2020-10-29T02:04:00.001-07:00

Exception Handling in Java

What is an Exception?

An exception is an unwanted or unexpected event, which occurs during the execution of a program i.e at run time, that disrupts the normal flow of the program’s instructions.

Error vs Exception

Error: An Error indicates serious problem that a reasonable application should not try to catch.
Exception: Exception indicates conditions that a reasonable application might try to catch.

Exception Hierarchy

All exception and errors types are sub classes of class Throwable, which is base class of hierarchy.One branch is headed by Exception. This class is used for exceptional conditions that user programs should catch. NullPointerException is an example of such an exception.Another branch,Error are used by the Java run-time system(JVM) to indicate errors having to do with the run-time environment itself(JRE). StackOverflowError is an example of such an error.

How JVM handle an Exception?

Default Exception Handling : Whenever inside a method, if an exception has occurred, the method creates an Object known as Exception Object and hands it off to the run-time system(JVM). The exception object contains name and description of the exception, and current state of the program where exception has occurred. Creating the Exception Object and handling it to the run-time system is called throwing an Exception.There might be the list of the methods that had been called to get to the method where exception was occurred. This ordered list of the methods is called Call Stack.Now the following procedure will happen.

The run-time system searches the call stack to find the method that contains block of code that can handle the occurred exception. The block of the code is called Exception handler.
The run-time system starts searching from the method in which exception occurred, proceeds through call stack in the reverse order in which methods were called.
If it finds appropriate handler then it passes the occurred exception to it. Appropriate handler means the type of the exception object thrown matches the type of the exception object it can handle.
If run-time system searches all the methods on call stack and couldn’t have found the appropriate handler then run-time system handover the Exception Object to default exception handler , which is part of run-time system. This handler prints the exception information in the following format and terminates program abnormally.

Exception in thread "xxx" Name of Exception : Description
... ...... ..  // Call Stack

Example :

// Java program to demonstrate how exception is thrown. 

class ExecptionExample{ 

    public static void main(String args[]){ 

        String str = null; 

        System.out.println(str.length()); 

    } 

}

Output :

Exception in thread "main" java.lang.NullPointerException
    at ExecptionExample.main(File.java:8)

How to use try-catch clause

try {
// block of code to monitor for errors
// the code you think can raise an exception
}
catch (ExceptionType1 exOb) {
// exception handler for ExceptionType1
}
catch (ExceptionType2 exOb) {
// exception handler for ExceptionType2
}
// optional
finally {
// block of code to be executed after try block ends
}

How Programmer handles an exception?

Customized Exception Handling :

Java exception handling is managed via five keywords: try, catch, throw, throws, and finally. Briefly, here is how they work. Program statements that you think can raise exceptions are contained within a try block. If an exception occurs within the try block, it is thrown. Your code can catch this exception (using catch block) and handle it in some rational manner. System-generated exceptions are automatically thrown by the Java run-time system. To manually throw an exception, use the keyword throw. Any exception that is thrown out of a method must be specified as such by a throws clause. Any code that absolutely must be executed after a try block completes is put in a finally block.

package com.exception.examples;

public class Unchecked_Demo {

public static void main(String args[]) {

try {

int num[] = {1, 2, 3, 4};

System.out.println(num[5]);

}catch(ArrayIndexOutOfBoundsException e) {

System.out.println("num[] has exceed limits");

e.printStackTrace();

}

Points to be Noted:

In a method, there can be more than one statements that might throw exception, So put all these statements within its own try block and provide separate exception handler within own catch block for each of them.
If an exception occurs within the try block, that exception is handled by the exception handler associated with it. To associate exception handler, we must put catch block after it. There can be more than one exception handlers. Each catch block is a exception handler that handles the exception of the type indicated by its argument. The argument, ExceptionType declares the type of the exception that it can handle and must be the name of the class that inherits from Throwable class.
For each try block there can be zero or more catch blocks, but only one finally block.
The finally block is optional.It always gets executed whether an exception occurred in try block or not . If exception occurs, then it will be executed after try and catch blocks. And if exception does not occur then it will be executed after the try block. The finally block in java is used to put important codes such as clean up code e.g. closing the file or closing the connection.

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Throw keywords in Exception Handling in Java

2020-10-29T02:00:00.003-07:00

Throw keywords in Exception Handling in Java

Java throw keyword

The Java throw keyword is used to explicitly throw an exception.
We can throw either checked or uncheked exception in java by throw keyword. The throw keyword is mainly used to throw custom exception. We will see custom exceptions later.
The syntax of java throw keyword is given below.

throw exception;

Let's see the example of throw IOException.

throw new IOException("sorry device error);

Example

Suppose You have a Voting system and the condition to vote is age should be greater then 18 so Code vill be like below.

Example

package com.exception.examples;

import java.util.Scanner;

public class VotingSystem {

public void vote() throws AgeException

{ Scanner s = new Scanner(System.in);

System.out.println("Enter your Age :");

int age = s.nextInt();

if(age < 18) {

throw new AgeException("Age is not vailid");

}else {

System.out.println("your Age is eligible for

voting");

}

System.out.println("hello ");

}

Here the program throw Custom Exception AgeException which is defile like below

Example

package com.exception.examples;

public class AgeException extends RuntimeException{

public AgeException(String msg){

super(msg);

}

public class Caller {

public static void main(String args[]){

VotingSystem vs = new VotingSystem();

vs.vote();

}

Output:

Exception in thread main com.exception.examples.AgeException :Age is not vailid

I Hope You Understand the Trow Keyword and how can we use it.

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Inheritance IS-A Relationship in Java

2020-10-29T01:55:00.002-07:00

Inheritance in Java

Inheritance in Java is a mechanism in which one object acquires all the properties and behaviors of a parent object. It is an important part of OOPs (Object Oriented programming system).

The idea behind inheritance in Java is that you can create new classes that are built upon existing classes. When you inherit from an existing class, you can reuse methods and fields of the parent class. Moreover, you can add new methods and fields in your current class also.

Inheritance represents the IS-A relationship which is also known as a parent-child relationship.

Why use inheritance in java

For Method Overriding (so runtime polymorphism can be achieved).
For Code Reusability.

The syntax of Java Inheritance

class Subclass-name extends Superclass-name
{
//methods and fields
}

The extends keyword indicates that you are making a new class that derives from an existing class. The meaning of "extends" is to increase the functionality.

In the terminology of Java, a class which is inherited is called a parent or superclass, and the new class is called child or subclass.

Types of inheritance in java

On the basis of class, there can be 5 types of inheritance in java: single, multilevel and hierarchical, hybrid and multilevel inheritance.

In java programming, multiple and hybrid inheritance is supported through interface only. We will learn about interfaces later.

Single Inheritance Example

When a class inherits another class, it is known as a single inheritance. In the example given below, Dog class inherits the Animal class, so there is the single inheritance.

File: MyInheritance.java

class Animal{
void eat(){System.out.println("eating...");}
}
class Dog extends Animal{
void bark(){System.out.println("barking...");}
}
class MyInheritance{
public static void main(String args[]){
Dog d=new Dog();
d.bark();
d.eat();
}}

Output:

barking...
eatin

Multilevel Inheritance Example

When there is a chain of inheritance, it is known as multilevel inheritance. As you can see in the example given below, BabyDog class inherits the Dog class which again inherits the Animal class, so there is a multilevel inheritance.

File: MyInheritance2.java

class Animal{
void eat(){System.out.println("eating...");}
}
class Dog extends Animal{
void bark(){System.out.println("barking...");}
}
class BabyDog extends Dog{
void weep(){System.out.println("weeping...");}
}
class MyInheritance2{
public static void main(String args[]){
BabyDog d=new BabyDog();
d.weep();
d.bark();
d.eat();
}}

Output:

weeping...
barking...
eating...

Hierarchical Inheritance Example

When two or more classes inherits a single class, it is known as hierarchical inheritance. In the example given below, Dog and Cat classes inherits the Animal class, so there is hierarchical inheritance.

File: MyInheritance3.java

class Animal{
void eat(){System.out.println("eating...");}
}
class Dog extends Animal{
void bark(){System.out.println("barking...");}
}
class Cat extends Animal{
void meow(){System.out.println("meowing...");}
}
class MyInheritance3{
public static void main(String args[]){
Cat c=new Cat();
c.meow();
c.eat();
//c.bark();//C.T.Error
}}

Output:

meowing...
eating...

Why does multiple inheritance is not supported in java?

To reduce the complexity and simplify the language, multiple inheritance is not supported in java.
Consider a scenario where A, B, and C are three classes. The C class inherits A and B classes. If A and B classes have the same method and you call it from child class object, there will be ambiguity to call the method of A or B class.
Since compile-time errors are better than runtime errors, Java renders compile-time error if you inherit 2 classes. So whether you have same method or different, there will be compile time error.

class A{
void msg(){System.out.println("Hello");}
}
class B{
void msg(){System.out.println("Welcome");}
}
class C extends A,B{//suppose if it were
public static void main(String args[]){
C obj=new C();
obj.msg();//Now which msg() method would be invoked?
}
}

Compile Time Error

I hope you understand the concept of Inheritance

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String Comparison, Concatenation and Substring

2020-10-29T01:40:00.004-07:00

String Comparison, Concatenation and
Substring

There's a lot to say about Strings, from the ways you can initialize them to the String Literal Pool, however in this article we'll focus on common operations, rather than the class itself.

Introduction

Simply put, a String is used to store text, i.e. a sequence of characters. Java's most used class is the String class, without a doubt, and with such high usage, it's mandatory for Java developers to be thoroughly acquainted with the class and its common operations.

Java String comparison

We can compare string in java on the basis of content and reference.

It is used in authentication (by equals() method),
sorting (by compareTo() method),
reference matching (by == operator) etc

There are three ways to compare string in java:

By equals() method
By = = operator
By compareTo() method

1.Java String equals()

The java string equals() method compares the two given strings based on the content of the string. If any character is not matched, it returns false. If all characters are matched, it returns true.

The String equals() method overrides the equals() method of Object class.

Internal implementation

public boolean equals(Object anObject) {
if (this == anObject) {
return true;
}
if (anObject instanceof String) {
String anotherString = (String) anObject;
int n = value.length;
if (n == anotherString.value.length) {
char v1[] = value;
char v2[] = anotherString.value;
int i = 0;
while (n-- != 0) {
if (v1[i] != v2[i])
return false;
i++;
}
return true;
}
}
return false;
}

Signature

public boolean equals(Object anotherObject)

Parameter

anotherObject :

another object i.e. compared with this string.

Returns

true if characters of both strings are equal otherwise false.

Overrides

equals() method of java Object class.

Java String equals() method example

public class EqualsExample{
public static void main(String args[]){
String s1="learnwithreshu";
String s2="learnwithreshu";
String s3="LEARNWITHRESHU";
String s4="python";
System.out.println(s1.equals(s2));//true because content and case is same
System.out.println(s1.equals(s3));//false because case is not same
System.out.println(s1.equals(s4));//false because content is not same
}}

Output

true
false
false

Java String equals() Method Example 2

The equals() method compares two strings and can be used in if-else control structure.

public class EqualsExample {
public static void main(String[] args) {
String s1 = "learnwithreshu";
String s2 = "learnwithreshu";
String s3 = "learnwithreshu";
System.out.println(s1.equals(s2)); // True because content is same
if (s1.equals(s3)) {
System.out.println("both strings are equal");
}else System.out.println("both strings are unequal");
}
}

OutPut

true
both strings are unequal

Java String equals() Method Example 3

Let's see one more example to test the equality of string present in the list.

import java.util.ArrayList;
public class EqualsExample3 {
public static void main(String[] args) {
String str1 = "Mukesh";
ArrayList<String> list = new ArrayList<>();
list.add("Ravi");
list.add("Mukesh");
list.add("Ramesh");
list.add("Ajay");
for (String str : list) {
if (str.equals(str1)) {
System.out.println("Mukesh is present");
}
}
}
}

Mukesh is present

2.The == Operator

When you use the equality operator with primitive types, you’re just comparing their values. Take a look at the following examples:

 // comparing ints
    int x, y;
    x = 10;
    y = 15;
  System.out.println(x == y); // prints 'false'

    // comparing chars
    char a, b;
    a = '\n';
    b = '\n';
  System.out.println(a == b); // prints 'true'

    // comparing booleans
    boolean t, f;
    t = true;
    f = false;
  System.out.println(t == f); // prints 'false'

Using the == Operator With Object Types

When it comes to object types, the == operator is used to perform a referential equality comparison. What does that mean? It means that when you use the operator with object types, what you’re actually doing is testing whether the two variables have references that point to the same space in memory. Even if the objects referenced by the variables are identical in regards to their values, the results will still be false. This is somewhat unintuitive, and it can be a source of confusion—and bugs—especially for beginners. Let’s illustrate that with a code example. Suppose you have a Person class, like the one below:

 public class Person {
 private final String name;

 private final int age;

 public String getName() {
 return name;
 }

 public int getAge() {
 return age;
 }

 public Person(String name, int age) {
 this.name = name;
 this.age = age;
 }
}

Now, consider the following main method:

 public static void main(String[] args) {
     Person p = new Person("Alice", 20);
     Person p2 = new Person("Alice", 20);
     System.out.println(p == p2);
}

What do you think our little program will print when we run it? If your answer is false, then you’ve got it right. But why is that the case?

It has to do with references. When we initialize the p variable, we create a new instance of the Person class, which will live somewhere in the memory. The content of p is a reference (an “address”) to the location where the object resides.

When we utilize the p2 variable, we create another instance of Person. However, this instance will live at a different location in memory, and it’s this location that gets assigned to the variable. When using the == operator to compare the variables, we’re actually comparing the references they store, which are obviously different, so we get false as a result.

When using the operator to compare object types, the arguments must be compatible. That means that you can compare arguments of the same type, but also of types that have a child/parent relationship. If the arguments aren’t of the same type neither extend from one another, and you’ll get a compiler error. An example would show this more clearly. Consider the excerpt of code below:

 public class Student extends Person {

    private final String school;

    public Student(String name, int age, String school) {
        super(name, age);
        this.school = school;
    }

    public String getSchool() {
        return school;
    }
}

The example above features a new class, Student, that extends from the Person class shown in the first example. Now, take a look at the example below, that shows how we can compare instances of the two classes:

  Person p = new Person("Alice", 20);
    Person p1 = new Person("Alice", 20);
    Student s = new Student("Alice", 20, "Hogwarts");
    Student s1 = new Student("Alice", 20, "Hogwarts");
    Person p2 = s;

    System.out.println(p == p1); // prints 'false'
    System.out.println(p2 == s); // prints 'true'
    System.out.println(s == s1); // prints 'false'
    System.out.println(p == s1); // prints 'false'
    System.out.println(p == "test"); // compiler error

The first comparison returns false. Both arguments have the same type (Person). They point to objects which have the exact same values for their fields. But even though their values are equal, they’re not the same objects. They don’t share the same place in memory, and that’s what the operator is comparing.

The second comparison results in true. Here we’re comparing two variables that are of different, but compatible types, since Person is the parent of Student. The comparison returns true because both variables point to the same object.

The third comparison checks two variables of type Student. The variables point to objects that have the exact same values. Yet, the comparison returns false, since the objects don’t share the same reference.

Following next, we have a comparison between an instance of Person and an instance of Student. The types are compatible, but the result is false since the objects the variables point to aren’t the same.

Finally, we have a comparison between an instance of Person and a string. Since these types aren’t compatible, we get a compiler error.

3.compareTo method

The compareTo() method lexicographically compares our String with another. The actual comparison of the two strings is based on the Unicode value of each character in the string. The method returns either a positive number, a negative number, or 0.

If all characters in our string were all lower case (or all uppercase) letters, the return value of the compareTo() method can be interpreted as "if the return value was negative, my string would come before the other string in a dictionary".

I emphasize the point that the letters would need to be in the same case, since the function might produce unexpected output otherwise.

The compareTo() method doesn't go through all the characters in our strings, it returns as soon as it reaches the end of any of the strings, or as soon as it finds a non-matching character. In which case the function returns (Unicode value of the mismatched character in our string) - (Unicode value of the mismatched character in the given string).

System.out.println("a".compareTo("a"));

System.out.println("a".compareTo("b"));

System.out.println("1".compareTo("12345678"));

System.out.println("2".compareTo("12345678"));

System.out.println("abcd".compareTo("abgggggggggg"));

Output :-

-1

-7

-4

On the third line of the code above, in this case compareTo returns the difference in string lengths, since it didn't find a mismatched character before it "ran out" of characters in one string.

And in the last line we see -4 is printed because of 'c' - 'g', since that's the first mismatch it found, and it doesn't care about the rest.

Note: The "unexpected" part when using compareTo() happens when we compare strings with different cases.

System.out.println("ORANGE".compareTo("apple"));

We might expect the method to return a positive value, since "apple" should come before "ORANGE". However, the Unicode value for 'O' is less than the Unicode value for 'a'.

This might sometimes be preferred behavior, but in case it isn't - we use compareToIgnoreCase(). That method does essentially the same thing as compareTo(), it just pretends that everything is in the same case, and gives us a "proper" dictionary order.

Note: compareTo() and compareToIgnoreCase() are often used when we make a Comparator for a custom class.

String Concatenation in Java

In java, string concatenation forms a new string that is the combination of multiple strings. There are two ways to concat string in java:

By + (string concatenation) operator
By concat() method

1) String Concatenation by + (string concatenation) operator

Java string concatenation operator (+) is used to add strings. For Example:

class TestStringConcatenation1{
public static void main(String args[]){
String s="Sachin"+" Tendulkar";
System.out.println(s);//Sachin Tendulkar
}
}

Output:Sachin Tendulkar

The Java compiler transforms above code to this:

String s=(new StringBuilder()).append("Sachin").append(" Tendulkar).toString();


2) String Concatenation by concat() method

The String concat() method concatenates the specified string to the end of current string. Syntax:

public String concat(String another)  


Let's see the example of String concat() method.

class TestStringConcatenation3{  
 public static void main(String args[]){  
   String s1="Sachin ";  
   String s2="Tendulkar";  
   String s3=s1.concat(s2);  
   System.out.println(s3);//Sachin Tendulkar  
  }  
}

Output:

Sachin Tendulkar
Substring in Java

A part of string is called substring. In other words, substring is a subset of another string.

In case of substring startIndex is inclusive and endIndex is exclusive.

You can get substring from the given string object by one of the two methods:
public String substring(int startIndex): This method returns new String object

containing the substring of the given string from specified startIndex (inclusive).
public String substring(int startIndex, int endIndex): This method returns new String object

containing the substring of the given string from specified startIndex to endIndex.

In case of string:
startIndex: inclusive
endIndex: exclusive

Let's understand the startIndex and endIndex by the code given below.

String s="hello";  
System.out.println(s.substring(0,2));//he

In the above substring, 0 points to h but 2 points to e (because end index is exclusive).

Example of java substring
public class TestSubstring{  
 public static void main(String args[]){  
   String s="SachinTendulkar";  
   System.out.println(s.substring(6));//Tendulkar  
   System.out.println(s.substring(0,6));//Sachin  
 }  
}

Output
Tendulkar
Sachin

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Primitive and Non Primitive Data types ,Difference between primitive and non-primitive data types

2020-10-29T01:24:00.002-07:00

Primitive and Non Primitive Data types

A data type is an attribute of a variable which tells the compiler or interpreter how the programmer intends to use the variables. It defines the operations that can be done on the data and what type of values can be stored. In this article, I will give you a brief insight into the different data types in java. According to the properties they possess, data types are divided into two groups:

Primitive Data Types
Non-Primitive Data Types

Primitive Data Types:

A primitive data type is pre-defined by the programming language. The size and type of variable values are specified, and it has no additional methods.

Non-Primitive Data Types:

These data types are not actually defined by the programming language but are created by the programmer. They are also called “reference variables” or “object references” since they reference a memory location which stores the data.

Now, let’s move further and get into the details of Primitive Data Types.

Primitive Data Types

Data types in Java are classified into 4 aspects as int, float, character and boolean. But, in general, there are 8 data types. They are as follows:

byte data type
boolean data type
char data type
short data type
int data type
long data type
float data type
double data type

You can refer to the below figure to understand the different data types with respect to the memory allocated to them, and there defaults values

That was all about the data type. I hope you understood it. Now let’s understand each of these data types in depth i.e. byte data type.

01. Byte data type

This is an example of a primitive data type. It is an 8-bit signed two’s complement integer. It stores whole numbers that lie between -128 to 127. A byte data type is helpful for saving memory in large amounts. Now let’s write a small program and understand how it works.

class ByteDatatype {

public static void main(String[] args) {

byte a, b;

a = 127;

b=177;

System.out.println(a); // prints 127

System.out.println(b); // throws an error because it cannot store more than 127 bits

}

}

Now let’s understand what is boolean data type.

02. boolean data type

A boolean data type comprises of a bit of information and can store only true or false values. This data type is used to track true/false conditions. Now let’s write a small program and understand how it works.

class boolean{

public static void main(String args[]){

boolean language = true;

boolean Number= false;

System.out.println(language);   // Output will be true

System.out.println(Number);  // Output will be false

}

}

That was all about the boolean data type. Now let’s move further and comprehend the following data type i.e. short

03. short data type

A short data type is greater than byte in terms of size and less than a integer. It stores the value that ranges from -32,768 to 32767. The default size of this data type: 2 bytes. Let’s take an example and understand the short data type.

1

2

3

4

5

6

class Short {

public static void main(String[] args) {

short c= 3435,

System.out.println(c); // prints the value present in n i.e. 3435

}

}

Moving ahead, let’s move further and look at the next data type i.e. i char data type

04. char data type

This data type is used to store a single character. The character must be enclosed within single quotes, like ‘F’ or ‘f’. Alternatively, you can also use ASCII values to display certain characters. Let’s take a small example and see how it works.

char  beta = 'J';

char a = 65, b = 66, c = 67;

System.out.println(beta ); // prints J

System.out.println(a); // Displays 65

System.out.println(b); // Displays 66

System.out.println(c); // Displays 67

That was all about the char data type. I hope you understood it. Now let’s move further and understand the next data type on the list i.e. long data type.

05. long data type

This data type is a 64-bit two’s complement integer. By default, the size of a long data type is 64 bit and its value ranges from -263 to 263-1.

For example:

long number = 15000000000L;

System.out.println(number ); // prints 15000000000

That was all about the long data type. Now let’s move and see int data types.

06. int data type

This data type can store whole numbers from -2147483648 to 2147483647. Generally, int is the preferred data type when you create variables. with a numeric value.

For example:

int number = 5464564;

System.out.println(number ); // prints 5464564

Having understood this, now let’s see which is the next data type in the list.

07. Floating Datatypes

You should use a floating point type whenever you need a number with a decimal, such as 8.88 or 3.14515.

01. float data type

This data type can store fractional numbers from 3.4e−038 to 3.4e+038. Note that you should end the value with an “f”. Let’s take a small example and understand this data type in a detailed manner.

float num =67;

System.out.println(num); // prints the floating number value

So this is how you can use the float data type. Now let’s see one more floating data type i.e. double

02. double data type

The double data type can store fractional numbers from 1.7e−308 to 1.7e+308. Note that you should end the value with a “d”:

double num = 79.678d;

System.out.println(num); // prints double value

That was all about Double data type and this brings us to the end of Primitive Datatypes. Now let’s figure out the difference between primitive and non-primitive data types.

Difference between primitive and non-primitive data types

The difference between primitive and non-primitive data types are as follows:

Primitive types are predefined in java. Non-primitive types are created by the programmer and is not defined by Java.
Non Primitive types can be used to call methods to perform certain operations, while primitive types cannot.
A primitive type always has a value, whereas non-primitive types can be null.
A primitive type starts with a lowercase letter, while non-primitive types start with an uppercase letter.
The size of a primitive type depends on the data type, while non-primitive types have all the same size.

Non-Primitive Datatypes

Non-Primitive data types refer to objects and hence they are called reference types. Examples of non-primitive types include Strings, Arrays, Classes, Interface, etc. Below image depicts various non-primitive data types.

Let’s now understand these non-primitive data types in short.

Strings:

String is a sequence of characters. But in Java, a string is an object that represents a sequence of characters. The java.lang.String class is used to create a string object.

Arrays:

Arrays in Java are homogeneous data structures implemented in Java as objects. Arrays store one or more values of a specific data type and provide indexed access to store the same. A specific element in an array is accessed by its index.

Classes:

A class in Java is a blueprint which includes all your data. A class contains fields(variables) and methods to describe the behavior of an object.

Structure:

Non-primitive not just store a value, but rather a collection of values in various formats

So that was all about the non-primitive data types.

I Hope you understand different types of data types and there differences For Explanation in hindi please visit my Youtube channel

In This blog I will explain about different types of Data types

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Types of Inheritance, what is Inheritance, different types of Constructors

2020-10-29T00:56:00.002-07:00

Types of Inheritance and Constructors

In this video I have explain full detail of Inheritance and constructor

Please watch the video and Learn something new!!!!!

Thanks for watching!!!

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Complete Guide for if else Statement.

2020-10-29T00:51:00.004-07:00

Complete Guide for if else Statement.

Java has the following conditional statements:

Use if to specify a block of code to be executed, if a specified condition is true
Use else to specify a block of code to be executed, if the same condition is false
Use else if to specify a new condition to test, if the first condition is false
Use switch to specify many alternative blocks of code to be executed

Java supports the usual logical conditions from mathematics:

Less than: a < b
Less than or equal to: a <= b
Greater than: a > b
Greater than or equal to: a >= b
Equal to a == b
Not Equal to: a != b

You can use these conditions to perform different actions for different decisions.

The if Statement

Use the if statement to specify a block of Java code to be executed if a condition is true.

Syntax

if (condition) {
  // block of code to be executed if the condition is true
}

Note that if is in lowercase letters. Uppercase letters (If or IF) will generate an error.

In the example below, we test two values to find out if 21 is greater than 19. If the condition is true, print some text:

Example

if (21 > 19) {
  System.out.println("21 is greater than 19");
}

As Same way we can also test variables:

Example

int x = 22;
int y = 20;
if (x > y) {
  System.out.println("x is greater than y");
}

Example explained

In the example above we use two variables, x and y, to test whether x is greater than y (using the > operator). As x is 22, and y is 20, and we know that 22 is greater than 20, we print to the screen that "x is greater than y".

No turn comes for

The else Statement

We use `else` statement to specify a block of code to be executed if the condition in if is `false`.

Syntax

if (condition) {
  // block of code to be executed if the condition is true
} else {
  // block of code to be executed if the condition is false

}

Example

int number = 10;
if (number > 18) {
  System.out.println("Hello.");
} else {
  System.out.println("Bye.");
}

// Outputs "Bye."

Example explained

In the example above, number (10) is less than 18, so the condition is false. Because of this, we move on to the else condition and print to the screen "Bye". If the number was greater than 18, the program would print "Hello".

The else if Statement

We use the else if statement to specify a new condition if the first condition defined in if is false.

Syntax

if (condition1) {
  // block of code to be executed if condition1 is true
} else if (condition2) {
  // block of code to be executed if the condition1 is false and condition2 is true
} else {
  // block of code to be executed if the condition1 is false and condition2 is false
}

Example

int number = 22;
if (number < 10) {
  System.out.println("Good morning.");
} else if (number < 20) {
  System.out.println("Good day.");
} else {
  System.out.println("Good evening.");
}
// Outputs "Good evening."

Example explained

In the example above, number (22) is greater than 10, so the first condition is false. The next condition, in the else if statement, is also false, so we move on to the else condition since condition1 and condition2 is both false - and print to the screen "Good evening".

However, if the number was 14, our program would print "Good day."

Nested If Else statement

Please click on play and learn if else statement for free with good code example..

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·       Using throw, catch and instanceof to handle Exceptions in Java
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·       Overloading in Java
·       Interfaces in Java
·       Loops in Java
·       Variables in Java

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·       Encapsulation in java
·       Learn Complete OOPS Concepts in one Project
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Introduction of String

2020-09-17T02:18:00.006-07:00

Introduction of String

In Java, string is basically an object that represents sequence of char values. An array of characters works same as Java string.

For example:

char[] ch={’l',’e',’a',’r',’w',’i',’t',’h',’r',’e’,’s’,’h’,’u’};

String s=new String(ch);

is same as:

String s=”learnwithreshu";

The java.lang.String class implements Serializable, Comparable and CharSequence interfaces.

What is String in java?

Generally, String is a sequence of characters. But in Java, string is an object that represents a sequence of characters. The java.lang.String class is used to create a string object. then Question arises that

How to create a string object?

There are two ways to create String object:

By string literal

By new keyword

String Literal

Java String literal is created by using double quotes.

For Example:

String s=”Reshu";

Each time you create a string literal, the JVM checks the "string constant pool" first. If the string already exists in the pool, a reference to the pooled instance is returned. If the string doesn't exist in the pool, a new string instance is created and placed in the pool. For example:

String s1=“Welcome";

String s2=“Welcome";

s2 doesn't create a new instance

String objects are stored in a special

memory area known as the

"string constant pool".

By new keyword

In such case, JVM will create a new string object in normal (non-pool) heap memory, and the literal "Welcome" will be placed in the string constant pool. The variable s will refer to the object in a heap (non-pool).

String s=new String("Welcome"); //creates two objects and one reference variable

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Java IO Tutorial

2020-09-17T01:30:00.004-07:00

Java IO Tutorial

Hi Friends In, this tutorial i will going to explain about Java I/O. Basically Java I/O (Input and Output) is used to process the input and produce the output. Java uses the concept of a stream to make I/O operation fast. The java.io package contains all the classes required for input and output operations.

Java IO Overview

A good place to start learning about Java IO is the Java IO Overview tutorial. That tutorial gives you a quick overview of the central concepts in the Java IO API, and an overview of all the central classes in the Java IO API.

Java IO is an API that comes with Java which is targeted at reading and writing data (input and output). Most applications need to process some input and produce some output based on that input. For instance, read data from a file or over network, and write to a file or write a response back over the network.

The Java IO API is in the Java IO package (java.io). If you look at the Java IO classes in the java.io package the vast amount of choices can be rather confusing. What is the purpose of all these classes? Which one should you choose for a given task? How do you create your own classes to plugin? etc.

The purpose of this tutorial is to try to give you an overview of how all information related to Java I/O and the classes which are grouped in this package, and the purpose behind them, so you don't have to wonder whether you chose the right class, or whether a class already exists for your purpose.

The java.io package contains nearly every class you might ever need to perform input and output (I/O) in Java. All these streams represent an input source and an output destination. The stream in the java.io package supports many data such as primitives, object, localized characters, etc.

Java IO Class Overview Table

Here is a table listing most (if not all) Java IO classes divided by input, output, being byte based or character based, and any more specific purpose they may be addressing, like buffering, parsing etc.

Stream

A stream can be defined as a sequence of data.

There are two kinds of Streams −

InPutStream − The InputStream is used to read data from a source.

OutPutStream − The OutputStream is used for writing data to a destination.

Byte Streams

Java byte streams are used to perform input and output of 8-bit bytes. Though there are many classes related to byte streams, but the most frequently used classes are, FileInputStream and FileOutputStream. Following is an example which makes use of these two classes to copy an input file into an output file −

Example

import java.io.*;
public class CopyFileTo {

   public static void main(String args[]) throws IOException {  
      FileInputStream in = null;
      FileOutputStream out = null;



      try {
         in = new FileInputStream("input.txt");
         out = new FileOutputStream("output.txt");
         
         int c;
         while ((c = in.read()) != -1) {
            out.write(c);
         }
      }finally {
         if (in != null) {
            in.close();
         }
         if (out != null) {
            out.close();
         }
      }
   }
}

Now let's have a file input.txt with the following content −

This is test for copy file.

As a next step, compile the above program and execute it, which will result in creating output.txt file with the same content as we have in input.txt. So let's put the above code in CopyFile.java file and do the following −

$javac CopyFile.java
$java CopyFile

Character Streams

Java Byte streams are used to perform input and output of 8-bit bytes, whereas Java Character streams are used to perform input and output for 16-bit unicode. Though there are many classes related to character streams, but the most frequently used classes are, FileReader and FileWriter. Though internally FileReader uses FileInputStream and FileWriter uses FileOutputStream but here the major difference is that FileReader reads two bytes at a time and FileWriter writes two bytes at a time.

We can re-write the above example, which makes the use of these two classes to copy an input file (having unicode characters) into an output file −

Example

import java.io.*;
public class CopyFileTo {

   public static void main(String args[]) throws IOException {
      FileReader in = null;
      FileWriter out = null;

      try {
         in = new FileReader("input.txt");
         out = new FileWriter("output.txt");
         
         int c;
         while ((c = in.read()) != -1) {
            out.write(c);
         }
      }finally {
         if (in != null) {
            in.close();
         }
         if (out != null) {


            out.close();
         }
      }
   }
}

Now let's have a file input.txt with the following content -

This is test for copy file.

$javac CopyFile.java
$java CopyFile

Reading and Writing File

As described earlier, a stream can be defined as a sequence of data. The InputStream is used to read data from a source and the OutputStream is used for writing data to a destination.

The two important streams are FileInputStream and FileOutputStream, which would be discussed in this tutorial.

FileInputStream

This stream is used for reading data from the files. Objects can be created using the keyword new and there are several types of constructors available.

Following constructor takes a file name as a string to create an input stream object to read the file –

InputStream f = new FileInputStream("C:/java/hello");

Following constructor takes a file object to create an input stream object to read the file. First we create a file object using File() method as follows File f = new File("C:/java/hello");

InputStream f = new FileInputStream(f);

Once you have InputStream object in hand, then there is a list of helper methods which can be used to read to stream or to do other operations on the stream.

There are other important input streams available, for more detail you can refer to the following links −

ByteArrayInputStream

DataInputStream

FileOutputStream

FileOutputStream is used to create a file and write data into it. The stream would create a file, if it doesn't already exist, before opening it for output.

Here are two constructors which can be used to create a FileOutputStream object.

Following constructor takes a file name as a string to create an input stream object to write the file −

OutputStream f = new FileOutputStream("C:/java/hello")

Following constructor takes a file object to create an output stream object to write the file. First, we create a file object using File() method as follows −

File f = new File("C:/java/hello");

OutputStream f = new FileOutputStream(f);

Once you have OutputStream object in hand, then there is a list of helper methods, which can be used to write to stream or to do other operations on the stream.

There are other important output streams available, for more detail you can refer to the following links −

ByteArrayOutputStream

DataOutputStream

Example

Following is the example to demonstrate InputStream and OutputStream −

import java.io.*;
public class fileStream {



   public static void main(String args[]) {
   
      try {
         byte bWrite [] = {11,21,3,40,5};
         OutputStream os = new FileOutputStream("test1.txt");
         for(int x = 0; x < bWrite.length ; x++) {
            os.write( bWrite[x] );   // writes the bytes
         }
         os.close();
     
         InputStream is = new FileInputStream("test2.txt");
         int size = is.available();



         for(int i = 0; i < size; i++) {
            System.out.print((char)is.read() + "  ");
         }
         is.close();
      } catch (IOException e) {
         System.out.print("Exception");
      }	
   }
}

The above code would create file test.txt and would write given numbers in binary format. Same would be the output on the stdout screen.

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Java Program for Add Two Dates with time

2020-09-07T03:25:00.001-07:00

Java Program for Add Two Dates with time

In this program, I am going to explain how to add two dates in Java using Calendar.

If you want understand this example, you should have the knowledge of the following Java programming topics:

Java Basic Input and Output
Java Class and Objects

Since, Java epoch is 1970, any time represented in a Date object will not work. This means, your Dates will start from 1970 and when two Date objects are added, the sum misses by about 1970 years. So, we use Calendar instead.

Example: Java program for add two dates

import java.util.Calendar;

public class AddDatesandtime {

    public static void main(String[] args) {

        Calendar c1 = Calendar.getInstance();
        Calendar c2 = Calendar.getInstance();
        Calendar cTotal = (Calendar) c1.clone();

        cTotal.add(Calendar.YEAR, c2.get(Calendar.YEAR));
        cTotal.add(Calendar.MONTH, c2.get(Calendar.MONTH) + 1); // Zero-based months
        cTotal.add(Calendar.DATE, c2.get(Calendar.DATE));
        cTotal.add(Calendar.HOUR_OF_DAY, c2.get(Calendar.HOUR_OF_DAY));
        cTotal.add(Calendar.MINUTE, c2.get(Calendar.MINUTE));
        cTotal.add(Calendar.SECOND, c2.get(Calendar.SECOND));
        cTotal.add(Calendar.MILLISECOND, c2.get(Calendar.MILLISECOND));

        System.out.format("%s + %s = %s", c1.getTime(), c2.getTime(), cTotal.getTime());

    }
}

Output

Mon Sep 07 12:22:38 CEST 2020 + Mon Sep 07 12:22:38 CEST 2020 = Sat Jun 15 00:45:16 CEST 4041

In the above program, c1 and c2 stores the current date. Then, we simply clone c1 and add c2's each DateTime properties one after the other.

As you can see, we've added 1 to the months. This is because months start with 0 in Java.

Advanced Java Programming

2020-08-31T12:43:00.002-07:00

Advanced Java Programming

Advanced Java Programming :-

Introduction to advance java

As most of us already know that if we want to make normal applications it can be easily built using core Java concepts. But, when it we need to develop web applications, advanced Java fundamentals, like JSP, Servlets, JDBC etc. needed, so to add capabilities and features of the application advance java is essential for developers. Through the motive of this blog is to explain about Advanced Java, I will be giving you a complete insight into the fundamental concepts of Advance Java.

Figure - 1.2

If you want to see complete video on this please have a look the video below.

Learn with Reshu

Advanced Java Programming Course

Figure - 1.3

I hope you understood by the slide why Advanced Java is essential. For your better understanding, I have divided this article into two sections. Each of these section deals with one of the most important concepts of advanced Java:

JDBC (Java DataBase Connectivity
Java Servlets

So, now let’s begin our discussion and understand the concept of Java Database Connectivity, a helpful tool to interact with the database.

Figure - 1.4

Common JDBC Components

The JDBC API provides the following interfaces and classes −

DriverManager is used to manage a list of database drivers. The first driver that recognizes a certain subprotocol under JDBC will be used to establish a database Connection.
Driver is an interface that handles the communications with the database server. It also abstracts the details associated with working with Driver objects.
Connection is an interface that consists all the methods required to connect to a database. The connection object represents communication context, i.e., all communication with the database is through connection object only.

JDBC Driver Types

Figure - 1.5

Figure - 1.6

Figure - 1.7

Figure - 1.8

Figure - 1.9

Figure - 2.0

Figure - 2.1

Now let’s move on to the next topic and look at the steps required to create a JDBC Application.

Figure - 2.2

Figure - 2.3

Figure - 2.4

Figure - 2.5

Figure - 2.6

Figure - 2.7

Figure - 2.8

Figure - 2.9

Code Example is given below

package com.jdbc.eamples;

import java.sql.*;

public class MyDatabase {

static final String JDBC_DRIVER = "com.mysql.jdbc.Driver";

static final String DB_URL = "jdbc:mysql://localhost/databasename";

static final String USER = "your root username";

static final String PASS = "your root password";

public static void main(String[] args) {

Connection conn = null;

Statement stmt = null;

try {

Class.forName("com.mysql.cj.jdbc.Driver");

System.out.println("Connecting to database...");

conn = DriverManager.getConnection(DB_URL,"USER",PASS);

System.out.println("Creating statement...");

stmt = conn.createStatement();

//first inserting data in table

String sql= "INSERT INTO emp VALUES (101, 'Taylor', 'Swift', 30)";

stmt.executeUpdate(sql);

sql= "INSERT INTO emp VALUES(102, 'Linkin', 'Park', 28)";

stmt.executeUpdate(sql);

System.out.println("Inserted records into the table...");

System.out.println("Creating statement...");

System.out.println("database connected");

//then fetching data from table

sql = "SELECT idemp, first, last, age FROM emp";

ResultSet rs = stmt.executeQuery(sql);

//STEP 5: Extract data from result set

while(rs.next()){

//Retrieve by column name

int id = rs.getInt("idemp");

int age = rs.getInt("age");

String first = rs.getString("first");

String last = rs.getString("last");

//Display values

System.out.print("ID: " + id);

System.out.print(", Age: " + age);

System.out.print(", First: " + first);

System.out.println(", Last: " + last);

}

//STEP 6: Clean-up environment

rs.close();

stmt.close();

conn.close();

} catch(SQLException se){

//Handle errors for JDBC

se.printStackTrace();

}catch(Exception e){

//Handle errors for Class.forName

e.printStackTrace();

}finally{

//finally block used to close resources

try{

if(stmt!=null)

stmt.close();

}catch(SQLException se2){

}// nothing can be done

try{

if(conn!=null)

conn.close();

}catch(SQLException se){

se.printStackTrace();

}//end finally try

}//end try

System.out.println("Goodbye!");

}//end main

}

Introduction to Servlets

A servlet is a java programming language class that is used to extend the capabilities of servers that host applications accessed by means of a request-response programming model. Although servlets can respond to any type of request, they are commonly used to extend the applications hosted by web servers.

Servlet can be described as follows:

1. Servlet is a technology which is used to create a web application.

It is an API that provides many interfaces and classes including documentation.
Servlet is an interface that must be implemented for creating any Servlet.
It is also a class that extends the capabilities of the servers and responds to the incoming requests. It can respond to any requests.

Client Server Architecture

Complete Servlet Life Cycle

Create a dynamic Web Project using Servlet

Code example is given below

There are one Servlet in this project and one html page. In WEB-INF folder there is one web.xml file is present.

In com.reshu package there is a Servlet file SumServlet present the work of this servlet is to take values of two numbers from request object given by server and then add those two numbers and show the addition to the page in the form of response to the html page

package com.reshu;

import java.io.IOException;

import java.io.PrintWriter;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

public class SumServlet extends HttpServlet {

public void doPost(HttpServletRequest req, HttpServletResponse res) throws IOException{

int i = Integer.parseInt(req.getParameter("num1"));

int j = Integer.parseInt(req.getParameter("num2"));

int k = i+j;

PrintWriter out = res.getWriter();

out.println("result is " + k);

}

Here below is the code of html page by which user send request to the SumServlet

the code given below is for web.xml file for servlet-mapping. In

web.xml file their is a mapping for Servlet and html page by which when user submit the page request call the servlet according to mapping in this file. In this case SumServlet.

Web.xml

I hope you have enjoy my blog and please visit my youtube Channel for more videos in hindi.

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Encapsulation in java

2020-07-29T00:13:00.003-07:00

Encapsulation in java

Encapsulation

The meaning of Encapsulation, is to make sure that "sensitive" data is hidden from users. To achieve this, you must:

declare class variables/attributes as `private`

provide public get and set methods to access and update the value of a `private` variable

Get and Set

You learned from the previous blogs that `private` variables can only be accessed within the same class (an outside class has no access to it). However, it is possible to access them if we provide public get and set methods.

The `get` method returns the variable value, and the `set` method sets the value.

Syntax for both is that they start with either `get` or `set`, followed by the name of the variable, with the first letter in upper case:

Example

package com.encapsulation.examples;

public class MyEncapsulation {
 
  private String name;
  private String idNum;
  private int age;
   
 public String getName() {
  return name;
 }
 
 public void setName(String name) {
  this.name = name;
 }

 public String getIdNum() {
  return idNum;
 }

 public void setIdNum(String idNum) {
  this.idNum = idNum;
 }

 public int getAge() {
  return age;
 }

 public void setAge(int age) {
  this.age = age;
 }
 
}

public class Test {

 public static void main(String args[]) {
 
  MyEncapsulation me = new MyEncapsulation();
  
  me.setAge(50);
  
  me.setIdNum("AB123");
  
  me.setName("Reshu");
  
  System.out.println("Name : " + me.getName() + " Age : " + me.getAge() + " Id : "+ me.getIdNum());
  
  
 }

Example explained

The get method returns the value of the variable name.

The set method takes a parameter (name) and assigns it to the name variable. The this keyword is used to refer to the current object.

However, as the name variable is declared as private, we cannot access it from outside this class:

Example

public class Test{
  public static void main(String[] args) {
     MyEncapsulation me = new MyEncapsulation();

      me.name = "John";  // error
    System.out.println(me.name); // error 
  }
}

If the variable was declared as public, we would expect the following output:

John

but, as we try to access a private variable, we get an error:


Test.java:4: error: name has private access in MyEncapsulation             me.name = "John";                                             

  ^

Test.java:5: error: name has private access in MyEncapsulation   

System.out.println(me.name);                                                                    ^                                           

2 errors

Instead, we use the getName() and setName() methods to acccess and update the variable:

Example

public class Test{
  public static void main(String[] args) {
   MyEncapsulation me = new MyEncapsulation();

    me.setName("John"); // Set the value of the name variable to "John"
    System.out.println(me.getName());
  }
}

// Outputs "John"

Why Encapsulation?

Better control of class attributes and methods
Class attributes can be made read-only (if you only use the get method), or write-only (if you only use the set method)
Flexible: the programmer can change one part of the code without affecting other parts
Increased security of data

For Complete Explanation of this topic in hindi Please visit My Youtube Channel

Thanks For Watching!!!

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Polymorphism in Java Method Overriding and Method OverLoading in Java

2020-07-29T00:07:00.001-07:00

Polymorphism in Java Method Overriding and Method OverLoading in Java

Java Polymorphism

Polymorphism means "many forms", and it occurs when we have many classes that are related to each other by inheritance.

Like we specified in the previous Blog; Inheritance lets us inherit attributes and methods from another class. Polymorphism uses those methods to perform different tasks. This allows us to perform a single action in different ways.

Polymorphism are two types

Method Overriding : It calls as compile time polymorphism or static or early binding.

Method Overloading: It calls as Runtime polymorphism or dynamic or late binding.

For example, think of a superclass called Animal that has a method called animalSound(). Subclasses of Animals could be Pigs, Cats, Dogs, Birds - And they also have their own implementation of an animal sound (the pig oinks, and the cat meows, etc.): This is a example of Method overriding in Polymorphism.

Example

class Animal {
  public void animalSound() {
    System.out.println("The animal makes a sound");
  }
}

class Pig extends Animal {
  public void animalSound() {
    System.out.println("The pig says: wee wee");
  }
}

class Dog extends Animal {
  public void animalSound() {
    System.out.println("The dog says: bow wow");
  }
}

Now we can create Pig and Dog objects and call the animalSound() method on both of them:

class Animal {
  public void animalSound() {
    System.out.println("The animal makes a sound");
  }
}

class Pig extends Animal {
  public void animalSound() {
    System.out.println("The pig says: wee wee");
  }
}

class Dog extends Animal {
  public void animalSound() {
    System.out.println("The dog says: bow wow");
  }
}

class MyMainClass {
  public static void main(String[] args) {
    Animal myAnimal = new Animal();  // Create a Animal object
    Animal myPig = new Pig();  // Create a Pig object
    Animal myDog = new Dog();  // Create a Dog object
    myAnimal.animalSound();
    myPig.animalSound();
    myDog.animalSound();
  }
}

Method Overriding

In Method Overriding the overridden method has same name but different arguments as number of arguments Sequence of arguments or type of arguments would be different.

In The example below the Class Adder has three add method with different arguments this is a example of method overriding.

package com.polymorphism.examples;

public class Adder {
 
 void add(double a, int b) {
  
  System.out.println(a+b); 
 }
   
 void add(int b, double a) {
  
  System.out.println(a+b);
  
   System.out.println("Sequence changed");
 }
   void add(int a, int b) {
   
    System.out.println("no arguments");
 }
   
   public static void main(String[] args) {
    
    Adder test = new Adder();
      test.add(4,7);
      test.add(3.3, 7);
      test.add(8 , 4.9 );
   }
   
}

There are some Difference between Method Overriding And Method Overloading

Difference Between Method Overloading and Method Overriding

Example of Polymorphism

For Complete Explanation in Hindi Please visit My Youtube Channel

Complete Explanation on Method Overloading In Hindi

Complete Explanation on Method Overriding In Hindi

Thanks For Watching!!!

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Learn Complete OOPS Concepts in one Project

2020-07-28T23:53:00.004-07:00

Learn Complete OOPS Concepts in one Project

In this Page i will give a example Code for covering all oops concepts in only one single project.

Class Model

Code Example

Explanation:-

Suppose there is a Organization which has many departments and many Employees Some Employees are Part of Some Departments So In this Code example What i have created is A Organization Class Which is having Many Employees so One Employee Class and Employee is a part of Departments so We have Created one Departments ClassNow Organization, Department and Employee has some task to be done so for that i have created Interfaces for each one where i Have Defined tasks to be done by theses classes.

1. Organization.java

In This Organization Class below I have used Encapsulation concept to create getters and setters same i have created one default constructor and some variable of all kind of datatypes. I have created private methods as getters and setters.

package com.all.examples;

     public class Organization {

 Organization(){

 }

 //Encapsulation

    private static String name = "Learn With Reshu";

 private int id;

 private boolean status;

 private char grade;

 private int numberOfEmployee;

 private double growth; 

 public int getId() {

  return id;

 }

 public void setId(int id) {

  this.id = id;

 }

 public boolean isStatus() {

  return status;

 }

 public void setStatus(boolean status) {

  this.status = status;

 }

 public char getGrade() {

  return grade;

 }

 public void setGrade(char grade) {

  this.grade = grade;

 }

 public double getGrowth() {

  return growth;

 }

 public void setGrowth(double growth) {

  this.growth = growth;

 }

 public int getNumberOfEmployee() {

  return numberOfEmployee;

 }

 public void setNumberOfEmployee(int numberOfEmployee) {

  this.numberOfEmployee = numberOfEmployee;

 }

 public String getName() {

  return name;

 }

}

2. Employee.java :-

In Employee class I have created one Parametrized Construction having two parameters growthrate and name and created some private getters and setters with variables defined.

package com.all.examples;

public class Employee {

      Employee(double growthrate, String name){

       this.growthRate= growthrate;

       this.name = name;

 }

    private String name;

   private int id;

   private boolean status;

   private char grade;

   private double salary;

   private double growthRate; 

   public String getName() {

  return name;

 }

 public void setName(String name) {

  this.name = name;

 }

 public int getId() {

  return id;

 }

 public void setId(int id) {

  this.id = id;

 }

 public boolean isStatus() {

  return status;

 }

 public void setStatus(boolean status) {

  this.status = status;

 }

 public char getGrade() {

  return grade;

 }

 public void setGrade(char grade) {

  this.grade = grade;

 }

 public double getSalary() {

  return salary;

 }

 public void setSalary(double salary) {

  this.salary = salary;

 }

 public double getGrowthRate() {

  return growthRate;

 }

 public void setGrowthRate(double growthRate) {

  this.growthRate = growthRate;

 }

}

3. CallDepartments.java :- In this example Calldepartments.java class is used to show how can we extends abstract class Departments and how can we override methods by this example i have explained about method overriding concepts of Polymorphism in the method statusOfDeparment()

package com.all.examples;

public class CallDepartments extends Departments {

 @Override

 public void statusOfDepartment() {

        CallDepartments cd = new CallDepartments();

  cd.setStatus("Active");

  System.out.println("Department status is " + cd.getStatus());

 }

}

4 Departments.java :-

Departments class is a Abstract class by this i am showing how can we define abstract class and abstract method statusOfDepartment() which i have override in CallDeparments class.

 package com.all.examples;

public abstract class Departments {

 private String status ;

 public String getStatus() {

  return status;

 }

 public void setStatus(String status) {

  this.status = status;

 }

 public abstract void statusOfDepartment();

}

5. IOrganization.java, IDepartments and IEmployee :-

By this Interface i have defined some static final variables and abstract methods and public methods IDepartments interface is extending IEmployee, IOrganization Interfaces so by this way i have shown how can we extends Interfaces.

 package com.all.examples;

import java.util.List;

public interface IOrganization {

public float revanuPerYear(List employees);

 public char gradeOfOrganization(Organization organization);

 public boolean statusOfCompany(Organization organization);

}

package com.all.examples;

public interface IEmployee {

 public static final char gradeAEmployee = 'A';

 public static final char gradeBEmployee = 'B';

 public static final char gradeCEmployee = 'C';

 public abstract double salaryPerMonth(Employee employee);

 public boolean jobStatus(int id);

 public char GradeOfEmployee(double Salary);

}

 package com.all.examples;

public interface IDepartments extends IEmployee, IOrganization {

 public static final double gradeAEmployeeSalary = 2000;

 public static final double gradeBEmployeeSalary = 1000;

 public static final double gradeCEmployeeSalary = 500;

 public String nameOfDepartment(char grade); 

}

6. Main.java.-

Main.java class extends Departments Interface so bedefault it should implements the methods define in Departments Interface and because IDepartments Interface has extends IEmployee and IOrganization Interface so Main class needs to implements Methods define in IOrganization and IEmployee class as well.

package com.all.examples;

import java.util.ArrayList;

import java.util.List;

public class Main implements IDepartments{

public static double bonus = 8.3;

public static void main(String[] args) {

Organization organization = new Organization();

Main m = new Main();

Employee em = new Employee(70.5, "Reshu");

Employee em1 = new Employee(60.5, "Ria");

Employee em2 = new Employee(80.5, "Jiya");

List employees= new ArrayList();

employees.add(em);

employees.add(em1);

employees.add(em2);

for(Employee employee : employees) {

if(employee.getGrowthRate()==80.5) {

employee.setGrade(IEmployee.gradeAEmployee);

employee.setId(1);

}else if(employee.getGrowthRate()==70.5) {

employee.setGrade(IEmployee.gradeBEmployee);

employee.setId(1);

}else if(employee.getGrowthRate()==60.5){

employee.setGrade(IEmployee.gradeCEmployee);

employee.setId(3);

}

double salary = m.salaryPerMonth(employee);

boolean status= m.jobStatus(employee.getId());

m.GradeOfEmployee(salary);

System.out.println(employee.getName()+ " of "+ m.nameOfDepartment(employee.getGrade()) + "\n"+

" has grade "+employee.getGrade() + "\n"+ " has Id "+ employee.getId() + "\n"+ " of a Organization " + organization.getName() +

"\n"+ " has salary per month "+ salary + "\n"+ " and job status " + status );

System.out.println("\n");

}

organization.setNumberOfEmployee(employees.size());

System.out.println("Grade of a organization is " +

m.gradeOfOrganization(organization)+ " and " + " revanue is " + m.revanuPerYear(employees));

System.out.println("\n");

if( m.statusOfCompany(organization) == true) {

System.out.println("Organization is Active");

}else {

System.out.println("Organization is closed");

}

CallDepartments cd = new CallDepartments();

System.out.println("\n");

cd.statusOfDepartment();

}

@Override
public double salaryPerMonth(Employee employee) {
// TODO Auto-generated method stub

if(employee.getGrade()==IEmployee.gradeAEmployee) {

employee.setSalary(IDepartments.gradeAEmployeeSalary * bonus);

}else if(employee.getGrade()==IEmployee.gradeBEmployee) {

employee.setSalary(IDepartments.gradeBEmployeeSalary * bonus);

}else {

employee.setSalary(IDepartments.gradeCEmployeeSalary * bonus);
}

return employee.getSalary();
}

@Override
public boolean jobStatus(int id) {
// TODO Auto-generated method stub
boolean status;

if(id==1) {

status = true;
}else{

status = false;
}

return status;
}

@Override
public char GradeOfEmployee(double salary) {
// TODO Auto-generated method stub
char grade;

if(salary == (20000 * bonus)) {

grade=IEmployee.gradeAEmployee;

}else if (salary == (10000 * bonus)) {

grade=IEmployee.gradeBEmployee;
}else {

grade = IEmployee.gradeCEmployee;
}

return grade;
}

@Override
public float revanuPerYear(List employees) {
// TODO Auto-generated method stub
int numberofemployees = 0;
float revanue=0;
for(int i =0; i<=employees.size(); i++) {

numberofemployees++;
}
if(numberofemployees>2) {

revanue= 200000f;
}
return revanue;
}

@Override
public char gradeOfOrganization(Organization organization) {
// TODO Auto-generated method stub
if(organization.getNumberOfEmployee()< 2) {

organization.setGrade(IEmployee.gradeBEmployee);
return IEmployee.gradeBEmployee ;

}else {
organization.setGrade(IEmployee.gradeAEmployee);
return IEmployee.gradeAEmployee;

}

}

@Override
public boolean statusOfCompany(Organization organization) {
// TODO Auto-generated method stub

if(organization.getGrade()==IEmployee.gradeAEmployee) {

organization.setStatus(true);

return true;
}else {

organization.setStatus(false);
return false;
}

}

@Override
public String nameOfDepartment(char grade) {
// TODO Auto-generated method stub

if(grade== IEmployee.gradeAEmployee) {

return "Sales Department";

}else if(grade== IEmployee.gradeBEmployee) {

return "HR Department";

}else {

return "forth class employee";
}
}

}

So I hope you understand by this Code, how can we use different OOps concepts in Class and how can we implements those i different scenarios. If You want complete explanation in Hindi Please visit my Youtube Channel

For Complete explanation in Hindi please visit my Youtube Channel

Thanks For Watching!!!!

Recommended Posts:

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·       Built-in Exceptions in Java with examples

·       Using throw, catch and instanceof to handle Exceptions in Java

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·       Overloading in Java

·       Interfaces in Java

·       Loops in Java

·       Variables in Java

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·       Encapsulation in java

·   Primitive and Non Primitive Data types (Difference between primitive and non-primitive data types)

·       What is Java

·       Hello World Program in Java in Hindi

·       Install Java on Computer from beginning

·       Types of Inheritance and Constructors

·       How to use static keyword in Java

·       Complete Guide for if else Statement

·       Introduction of some maven commands

·       Hello World java program using Intellij

·       Enabling Remote Debug

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Variables in Java

2020-07-28T23:41:00.003-07:00

Variables in Java

Types of Variables In Java

How to initialize a variable?

In this way, a name can only be given to a memory location. It can be assigned values in two ways:

Variable Initialization : value assign like 20 in this case
Assigning value by taking input

datatype: Type of data that can be stored in this variable.
variable_name: Name given to the variable.
value: It is the initial value stored in the variable. for example 20 in this case.

How to declare a variable?

Type: Type of data that can be stored in this variable.
Variable Name: Name given to the variable.

There are three types of variables in Java:

Local Variables
Instance Variables
Static Variables

Local Variables

Static Variables or Class Variables

Instance Variable

Please visit My Youtube Channel to have complete tutorial on Variables and other OOPs Concepts in Java in Hindi

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What is Java

2020-07-17T00:05:00.006-07:00

What is Java

In this post i will going to explain about what is java in general. I have explained Java features OOps concepts, and some basic knowledge of Java code.

Please feel free to Like Share and Comments, You can always Subscribe my YouTube Channel and this Page as well in free to get more interesting videos...

Thanks for watching!!!!!

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Hello World Program in Java in Hindi

2020-07-16T11:26:00.005-07:00

Hello World Program in Java in Hindi

I have explain Hello world program in java, I have explain example code in hindi so that people who speaks hindi can understand easily. Please feel free to like share and subscribe my channel on youtube so that you can get notification first when i upload new videos..

Thanks for Watching!!!!!

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Install Java on Computer from beginning!...

2020-07-16T11:20:00.003-07:00

Install Java on Computer from beginning!...

First of all, you need to know which Operating system you need to install JAVA. There are 2 types of operating system I am discussing here given below.

1) Windows

2) MAC

Windows: -

Downloading and installing Java in windows is very easy and its does not costs anything. There are many ways to download Java for Windows

Online download: -

By this way you can use many online links or oracle website for downloading jdk of any version which you would like to download to your local system. But you need to have

Administrative permission to install Java on Microsoft Windows.

Download and Install

go to this link

https://www.oracle.com/technetwork/java/javase/downloads/jre8-downloads-2133155.html

click on the jdk version you need to install.

The File Download dialog box appears prompting you to run or save the download file

To run the installer, click Run.

To save the file for later installation, click Save As.

Choose the folder location and save the file to your local system.

Note: Save the file to a known location on your computer, for example, to your desktop.

Double-click on the saved file to start the installation process.

The installation process starts. Click the Install button to accept the license terms and to continue with the installation.

A few brief dialogs confirm the last steps of the installation process; click Close on the last dialog. This will complete Java installation process.

By this way you will going to have jdk install In your local system. But you need to fix many things before using java in your system.

1. Create JAVA_HOME environment variable.

2. Add path variable.

Lets learn how to create JAVA_HOME variable.

First type env variable in search tab in start menu. You will find the environment variable window to open.

Click on the window and it will look like this see picture

Then click on Environment Variable button the a new window will open like below image.

Click on new button and create JAVA_HOME variable like shown in the picture by entering these info

Given bellow.

Please write variable name as JAVA_HOME and variable value as Path to jdk folder and then click ok

By this way you will create JAVA_HOME variable.

Next step is to create path variable.

Ckick on path variable in the list and click edit and add JAVA_HOME AS shown in picture and click ok.

By this way you java will be install in the system properly.

For checking it please open command prompt and run command java -version and you will get the java version installed in your system.

And for confirmation

Mac:-

Java can be installed on from Mac versions 10.7.3 or later. A 64-bit browser for example Safari is required to run Oracle Java on Mac.

Install Java on Mac

Download the jre from

https://www.oracle.com/technetwork/java/javase/downloads/jre8-downloads-2133155.html

Review and agree to the terms of the license agreement before downloading the file.

The Install Wizard displays the Welcome to Java installation screen. Click Next

Double-click the .pkg file to launch it

Double-click on the package icon to launch install Wizard

After the installation has completed, a confirmation screen appears. Click Close to finish the installation process.

Set JAVA_HOME environment variable on Mac OS X

Here, we show you how to set $JAVA_HOME environment variable on latest Mac OSX.

Mac OSX 10.5 or later
In Mac OSX 10.5 or later, Apple recommends to set the $JAVA_HOME variable to /usr/libexec/java_home, just export $JAVA_HOME in file ~/.

bash_profile or ~/.profile.
$ vim .bash_profile
export JAVA_HOME=$(/usr/libexec/java_home)
$ source .bash_profile
$ echo $JAVA_HOME
/Library/Java/JavaVirtualMachines/1.7.0.jdk/Contents/Home

And to confirm if java installed in Mac or not run this command

/usr/libexec/java_home -V

Matching Java Virtual Machines (3):

1.7.0_05, x86_64: "Java SE 7"

/Library/Java/JavaVirtualMachines/1.7.0.jdk/Contents/Home

How to Install Java on You tube

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How to use static keyword in Java

2020-07-16T08:10:00.001-07:00

How to use static modifier in Java

There are some non-access modifiers to achieve many other functionalities in java.

· The static modifier for creating class methods and variables.

· The final modifier for finalizing the implementations of classes, methods, and variables.

· The abstract modifier for creating abstract classes and methods.

· The synchronized and volatile modifiers, which are used for threads.

The Static Modifier

Static Variables

The static keyword is used to create variables that will exist independently of any instances created for the class. Only one copy of the static variable exists regardless of the number of instances of the class.

Static variables are also known as class variables. Local variables cannot be declared static.

Static Methods

The static keyword is used to create methods that will exist independently of any instances created for the class.

Static methods do not use any instance variables of any object of the class they are defined in. Static methods take all the data from parameters and compute something from those parameters, with no reference to variables.

Class variables and methods can be accessed using the class name followed by a dot and the name of the variable or method.

Example

The static modifier is used to create class methods and variables, as in the following example

Class Employee.java

package com.statics.example;

public class Employee {

String name ;

static String company = "Learn With Reshu";

int id;

public Employee(String name,int id){

this.name= name;

this.id= id;

}

void display() {

System.out.println(this.name+" "+company+" "+this.id);

}

in the above example there is a class name Employee having static variable company

Class Test.java

package com.statics.example;

public class Test {

public static void main(String[] args) {

Employee em = new Employee("reshu", 001);

Employee em1 = new Employee("reshu1", 002);

Employee em2 = new Employee("reshu2", 003);

Employee em3 = new Employee("reshu3", 004);

em.display();

em1.display();

em2.display();

em3.display();

}

When we make a object of Employee class in Test Class and call display method so we do not need to enter value of company variable as its static value is define in once Employee class so it can use in Test class directly. this is a advantage of static modifier that we do not need to assign values many times once it has been assign and that can be call directly by Class reference.

I have explain here in this video how to use static keyword in java with very nice example code.

You can like share and subscribe my youchannel as well and get notification when i upload new videos..

Thanks for Watching !!!

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Learn With Reshu

Running and Building Gradle with Different JDKs - Sip of Java

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Abstraction in Java, How Abstraction works in java with example code

ClassObjects & MethodsInheritance(IS-A)HAS-A Relationship Association (adsbygoogle = window.adsbygoogle || []).push({}); AggregationCompositionPolymorphismMethod OverloadingMethod OverridingAbstraction in Java (Security)

What is Abstractionabstraction is a process of hiding the implementation details from the user, only the functionality will be provided to the user. In other words, the user will have the information on what the object does instead of how it does it.

What is Abstraction

How to achieve Abstraction

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Interface in Java

What is Interfaces

Java Interface Example

Loops in java With Example Code

LOOPS IN JAVA WITH EXAMPLE CODE

Java For Loop vs While Loop vs Do While Loop

02. For-each or Enhanced For Loop

03. Labeled For Loop

Java While Loop

Java do-while Loop

Exception Handling in Java

Exception Handling in Java

What is an Exception?

Throw keywords in Exception Handling in Java

Java throw keyword

The Java throw keyword is used to explicitly throw an exception.We can throw either checked or uncheked exception in java by throw keyword. The throw keyword is mainly used to throw custom exception. We will see custom exceptions later.The syntax of java throw keyword is given below.

throw exception; Let's see the example of throw IOException. throw new IOException("sorry device error);

Example

Example

Inheritance IS-A Relationship in Java

Inheritance in Java

Why use inheritance in java

The syntax of Java Inheritance

Types of inheritance in java

Single Inheritance Example

Multilevel Inheritance Example

Hierarchical Inheritance Example

Why does multiple inheritance is not supported in java?

String Comparison, Concatenation and Substring

String Comparison, Concatenation andSubstring

Internal implementation

Signature

Parameter

Overrides

equals() method of java Object class.

Java String equals() method example

Java String equals() Method Example 2

Java String equals() Method Example 3

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1) String Concatenation by + (string concatenation) operator

2) String Concatenation by concat() method

Example of java substring

Primitive and Non Primitive Data types ,Difference between primitive and non-primitive data types

Primitive and Non Primitive Data types

Primitive Data Types

That was all about the data type. I hope you understood it. Now let’s understand each of these data types in depth i.e. byte data type.

01. Byte data type

02. boolean data type

03. short data type

04. char data type

05. long data type

06. int data type

07. Floating Datatypes

01. float data type

02. double data type

Difference between primitive and non-primitive data types

Non-Primitive Datatypes

Strings:

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Types of Inheritance and Constructors

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Class
Objects & Methods
Inheritance(IS-A)
HAS-A Relationship Association

Aggregation
Composition
Polymorphism
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What is Abstraction
abstraction is a process of hiding the implementation details from the user, only the functionality will be provided to the user. In other words, the user will have the information on what the object does instead of how it does it.

The Java throw keyword is used to explicitly throw an exception.
We can throw either checked or uncheked exception in java by throw keyword. The throw keyword is mainly used to throw custom exception. We will see custom exceptions later.
The syntax of java throw keyword is given below.

throw exception;

Let's see the example of throw IOException.

throw new IOException("sorry device error);

String Comparison, Concatenation and
Substring

In this video I have explain full detail of Inheritance and constructor

Please watch the video and Learn something new!!!!!

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We use `else` statement to specify a block of code to be executed if the condition in if is `false`.

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The meaning of Encapsulation, is to make sure that "sensitive" data is hidden from users. To achieve this, you must:

declare class variables/attributes as `private`

provide public get and set methods to access and update the value of a `private` variable

You learned from the previous blogs that `private` variables can only be accessed within the same class (an outside class has no access to it). However, it is possible to access them if we provide public get and set methods.

The `get` method returns the variable value, and the `set` method sets the value.

Syntax for both is that they start with either `get` or `set`, followed by the name of the variable, with the first letter in upper case:

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