The Tech Matin

Java Vector Class

2018-11-24T21:23:00.000+05:30

Java Vector Class | Java Collection Vector Class

Vector is a class present in Java.util package, it is very similar to ArrayList but Vectoris synchronized and ArrayList is not synchronized. The Vector class underlying data structure is growable array, Vector class basically falls in legacy classes but now it is fully compatible with collection’s.

1. Vector implements a dynamic array that means it can grow as per requirement.

2. Like an array, it contains component that can be accessed by an index.

3. Vector class is similar to ArrayList but ArrayList is not synchronized and Vector class is synchronized.

4. Vector class is legacy and have some legacy methods that collection does not contain.

5. Vector class extends AbstractList and implements List interface in hierarchy.

Points about Vector class need to be remembered

1. Insertion order is preserved.

2. Duplicates are allowed.

3. Null is allowed.

4. Heterogeneous elements are allowed unlike array.

5. Implements List<E>, RandomAccess, Cloneable and Serilizable.

6. It is thread safe because methods are synchronized.

Vector Class Constructor

1) Vector v=new Vector();

It creates an empty Vector with initial capacity i.e., 10.

But when it reaches it max capacity then it creates a new Vector object with double of initial capacity, for example 10x2=20.

New Vector=Current Capacity x 2.

2) Vector v=new Vector(int c);

It creates a Vector object with specified initial capacity.

3)Vector v=new Vector(int c , int increment );

It creates a Vector object with specified initial capacity and with incremental capacity.

4) Vector v=new Vector(Collection c);

It creates an equivalent object for the given collection, means inter-conversion between collection object.

Now Vector Class Specific Methods

1) addElement(obj)

2) removeElement(obj)

3) removeElementAt(int i)

4) removeAllElement(int i)

Other methods are available by default from hierarchy.

Vector Class Example With Its Specific Methods, Using First Constructor.

import java.util.*;

public class VectorMethods {

public static void main(String[] args){

//default constructor with 10 initial capacity

Vector v=new Vector();

v.addElement(null);

v.addElement(1);

v.addElement("one");

v.addElement(2);

v.addElement("two");

System.out.println("After addElement "+v);

//removing null

v.removeElement(null);

System.out.println("After removal of some elements "+v);

//removing element from 0(Zero) index i.e.,1 ->here v contains[1, one, 2, two]

v.removeElementAt(0);

System.out.println("Now vector contains "+v);

//removing element from 1st index i.e.,2 ->here v contains[one, 2, two]

v.removeElementAt(1);

System.out.println("Now v contains "+v);

//now removing all elements

v.removeAllElements();

System.out.println("Empty Vector "+v);

}

Output:

After removal of some elements [1, one, 2, two]

Now vector contains [one, 2, two]

Now v contains [one, two]

Empty Vector []

Another Example Of Vector

In this example we have used methods add(obj) to add objects to end of the current vector ,

add(int index , obj) to add specific element at specified index, addAll(Collection c) to copy all elements of vector to another vector or list, add All(int index ,Collection c) to copy all elements of vector to another vector or list at specified index and clear() method to clear the vector, see below example.

import java.util.*;

public class VectorMethods{

public static void main(String[] args){

//default constructor

Vector v=new Vector();

v.add(1);

v.add("one");

v.add(2);

v.add("two");

System.out.println("v--->"+v);

//using add(int index, object)

v.add(0,0);

v.add(1,"zero");

System.out.println("v--->"+v);

//creating another vector and copying all elements of v to v_add

Vector v_add=new Vector();

//copying all elements of v to v_add using addAll(Collection c)

v_add.addAll(v);

System.out.println("v_add--->"+v_add);

//creating another vector

Vector v_add_at=new Vector();

v_add_at.add("x");

v_add_at.add("y");

//copying all elements of v_ad to v_add_at using addAll(intindex, Collection c)

v_add_at.addAll(2, v_add);

System.out.println("v_add_at--->"+v_add_at);

v_add_at.clear();

System.out.println("v_add_at after clear--->"+v_add_at);

}

Output:

v--->[1, one, 2, two]

v--->[0, zero, 1, one, 2, two]

v_add--->[0, zero, 1, one, 2, two]

v_add_at--->[x, y, 0, zero, 1, one, 2, two]

v_add_at after clear--->[]

Vector Example Using clone() and contains() Methods

In this example we used clone() method that returns the clone of this vector and contains() method to check whether a particular elements is present or not, it returns true if available or false if not available.

import java.util.*;

public class VectorMethods {

@SuppressWarnings({ "rawtypes", "unchecked" })

public static void main(String[] args){

//default constructor

Vector v=new Vector();

v.add("one");

v.add("two");

v.add("three");

System.out.println("Normal v--->"+v);

//default constructor

Vector v_clone=new Vector();

v_clone=(Vector)v.clone();

System.out.println("Clone of v"+v_clone);

//checking a particular element is present or not in v

System.out.println(v.contains("one"));

System.out.println(v.contains("four"));

}

Output:

Normal v--->[one, two, three]

Clone of v[one, two, three]

true

false

Try with remaining methods.

Hope it will help you.

Please write comments if you find anything incorrect, or share more information on this topics.

Encapsulation in java

2018-11-20T13:07:00.000+05:30

Encapsulation in Java

Encapsulation defines as the wrapping up of data into a single unit. It is the mechanism that binds code and data together which it manipulates. Also we can think about encapsulation as it a protective shield that protects the data from being accessed by the outside of this protected area.

In encapsulationvariables or data of a class is hidden from any other class and can be accessed only through any member functions of own class in which they are declared.

In encapsulation data is hidden from other classes, so it is also known as data-hiding.

In java encapsulationcan be achieved by making all the variables private and by writing public methods in the class to get and set the values of variables which is declared as private.

Java Bean classthe best example of a fully encapsulated class.

Advantages of Encapsulation

Data Hiding: The user will have no idea about inner implementation of the class and it will not be visible to users that how the class is storing the values in the variables. They only knows only we are passing the values to setter methods and variables get initialized with that values.

Increase flexibility: We can make the variables of the class as read only or write only depend on requirement. We can make variables read only by omit setter methods, if we want to make variables write-only then we need to omit getter methods.

Re-usability: Encapsulation also improves the reusability and easy to change with new requirements.

Testing code is easy: Encapsulated code is easy to test for unit testing.

Other advantages it provide the control over the data, suppose we want to set the value of id which should be greater than 100 only we can write the login inside the setter method.

A simple example of program to demonstrate encapsulation

public class MyClass {

//here variables are declared as private and

//these variables can only be accessed by public methods of class

private String name;

private int passport_no;

private int age;

//get method for name to access

public String getName() {

return name;

}

//set method for name to access

public void setName(String name) {

this.name = name;

}

//get method for passport_no to access

public int getPassport_no() {

return passport_no;

}

//set method for passport_no to access

public void setPassport_no(int passport_no) {

this.passport_no = passport_no;

}

//get method for age to access

public int getAge() {

return age;

}

//set method for age to access

public void setAge(int age) {

this.age = age;

}

In the above example in MyClass all the variables i.e., name,passpoer_no and age are declared as private to achieve encapsulation. The get methods like getName(),getPassport_no() and getAge() are aet as public ans these methods are used to access private variables. The set methods like setName(), setPassport_no() and setAge() are also public and used to access these variables to set the values of the variables.

Now the program to access the variables of the MyClass class is shown below.

public class TestMain {

public static void main(String[] args) {

MyClass obj=new MyClass();

//setting the values to variables

obj.setName("'The Tech Matin'");

obj.setPassport_no(123);

obj.setAge(23);

//getting the values

String name=obj.getName();

int passport_no=obj.getPassport_no();

int age=obj.getAge();

System.out.println(name+" "+passport_no+" "+age);

//obj.name;//error

//if try to direct access to name then we will get compile time error saying

//The field MyClass.name is not visible

}

Output:

'The Tech Matin' 123 23

Example of Read Only Class

public class MyClass{

//private college name

private String college="Elphinstone College";

//getter method to access

public String getCollege() {

return college;

}

Now we can not change the value of college.

Example of Write Only Class

public class MyClass{

//private college name

private String college="Elphinstone College";

//setter method

public voidsetCollege(String college) {

this.college = college;

}

Now we can not get the value of college.

See Also

Java Inheritance with simple example

Java Polymorphism with example

Java Abstraction with example

Abstraction in Java

2018-11-19T15:14:00.000+05:30

Abstraction in Java

In a simple word Abstraction means only key concept, for example we all are using TV remote and we know that how to on and off the TV by pressing a particular button but we don’t know how it does but we know it is used to on or off the TV.

In other words Abstraction is the process of hiding implementation details and showing only functionality to the users.

So Abstractionlets us focus on what the objects does instead of how it does it, refer above real world example.

How to achieve Abstraction in Java?

There are two ways to achieve abstraction Java.

1. Abstract class (It is known as 0 to 100% abstract class).

2. Interface (It is also known as 100% abstract class).

How to create an Abstract class in Java?

If a class declared as abstract keyword then it is known as an abstract class. It contains abstract and non-abstract method also. If we declare a class as abstract and it has some methods (may be abstract or concrete) then we need to extend this class and provide implementation according to requirement.

Important points to remember

1. If you want to create an abstract class then we need to declare this class as abstract.

2. It can have abstract methods as well as non-abstract methods too.

3. We can’t instantiate an abstract class.

4. It can have constructors and method also.

5. It can have final methods also which will restrict the child class to do any modification with its original body.

Example of an abstract class

A class which is declared as abstract known as abstract class.

abstract class X{}

Abstract Method in Java

A method which is declared as abstract and does not have body i.e., implementation is known as abstract method.

See this example.

Abstract void showDetails();

Example of Abstract class with an abstract method

In this example we have created an abstract class Cricketwith an abstract method play(),and we have provided its implementation in Sportclass.

abstract class Cricket{

abstract void play();

}

public class Sport extends Cricket{

@Override

void play() {

System.out.println("Playing Cricket");

}

public static void main(String[] args) {

Cricket obj=new Sport();

obj.play();

}

Output:

Playing Cricket

Another example of Abstract class in Java

In this example we have created an abstract class India with an abstract method state() and providing its implementation in sub classes i.e., Bihar,Upand Maharashtra classes.

abstract class India{

abstract void state();

}

class Bihar extends India{

@Override

void state() {

System.out.println("Hello I am from Bihar");

}

class Up extends India{

@Override

void state() {

System.out.println("Hello I am from UP");

}

class Maharshtra extends India{

@Override

void state() {

System.out.println("Hello I am from Maharashtra");

}

public class StateOfIndia{

public static void main(String[] args) {

India obj=new Bihar();

obj.state();

obj=new Up();

obj.state();

obj=new Maharshtra();

obj.state();

}

Output:

Hello I am from Bihar

Hello I am from UP

Hello I am from Maharashtra

Abstract class with constructor ,abstract method and non-abstract method

Here in this example we have created an abstract class India with constructor, an abstract method state() and a non-abstract method TestMethod(). We provided the implementation of state() method in sub class Bihar.

abstract class India{

public India() {

System.out.println("India class constructor");

}

abstract void state();

void TestMethod() {

System.out.println("Test Method Invoked");

}

class Bihar extends India{

@Override

void state() {

System.out.println("Hello I am from Bihar");

}

public class StateOfIndia{

public static void main(String[] args) {

India obj=new Bihar();

obj.state();

obj.TestMethod();

}

Output:

India class constructor

Hello I am from Bihar

Test Method Invoked

Note : An abstract class can have data members ,abstract methods, method body(Non-abstract method) , constructor and even main method also.

Abstract class with data members and with constructor

In this class we have created an abstract class MyClass with id, name, parameterized constructor and main method also, here we are using anonymous inner class to create an object of this class to access the members.

public abstract class MyClass{

private int id;

private String name;

public MyClass(int id, String name) {

this.id = id;

this.name = name;

}

public static void main(String[] args) {

MyClass obj=new MyClass(1,"Matin") {

};

System.out.println(obj.id+" "+obj.name);

}

Output:

1 Matin

We can achieve the same thing by creating a child class and main method in abstract class to create the object of abstract class see example carefully , here we are not using constructor.

Since we can not access the non-static member without creating an object of class, as we can not create the object of abstract class, so we need to create a concrete child class and use the this class to access the members of abstract class. For example,

public abstract class MyClass{

private int id=1;

private String name="Matin";

public static void main(String[] args) {

MyClass obj=new ChildClass();

System.out.println(obj.id+" "+obj.name);

}

class ChildClass extends MyClass{

}

Output: 1 Matin

See also
Java Inheritance with example
Java Polymorphism with example

Java Polymorphism

2018-11-18T18:01:00.001+05:30

What is Polymorphism in java?

Simple meaning of Polymorphism is more than one form.

The word Polymorphism is derived from two Greek words i.e., poly and morphs.

The word poly mean many/more and morphs means forms.

So Polymorphism means many forms or more than one form.

Types of Polymorphism in Java?

There are two types of Polymorphism in Java.

1. Compile Time Polymorphism.

2. Run Time Polymorphism.

What is Compile-Time Polymorphism in Java?

Compile time polymorphism or static method dispatch is a process in which a call to an overloadingmethod is resolved at compile time rather than at run time, in this process overloaded method is called through reference variable of current class here no need of super-class concept.

How to achieve Polymorphism in Java?

We can achieve Polymorphism in Java by two ways i.e., method overloading and method overriding.

What is Method Overloading in Java?

If a class contains multiple methods with same name but different parameters and with different parameter data types then it is known as Method Overloading.

Advantage of method overloading?

Increase the readability of the program.

Rule to overload a method?

1. You must change the number of arguments.

2. You must change the data type.

Example of method overloading.

· By changing the number of argument.

Class Sport{

void players(String player1, String player2){

System.out.println("Players with two argument invoked");

}

void players(String player1, String player2, String player3){

System.out.println("Players with three argument invoked");

}

· By changing data types.

Class Sport{

void players(String player1, int wickets){

System.out.println("Players with two argument invoked");

}

void players(String player1, double runs){

System.out.println("Players with three argument invoked");

}

What is Run-Time Polymorphism in Java?

Run-time polymorphism is a process in which we have to override a method and call to that overridden method is resolved at runtime rather than at compile-time.

In the process of Run-Time polymorphism, an overridden method is called through the super class reference variable. However determination of the method to be called is based on the object of class that is being referred by the reference variable.

Ex- Super-Class sc=new Child-Class();.

Here Super-Class reference variable is sc that is referred to the Child-Class object i.e., here Child-Class object will be created using the reference of Super-Class sc, This is the concept of up-casting in Java.

Up-Casting

If parent class reference variable refers to the object of child class then it is nothing but up-casting in Java , See example given below using class and interface type reference .

Class type reference variable.

Class X{}

Class Y extends X{}

X obj=new Y();//up-casting

Interface type reference variable.

Interface I{}

Class X{}

Class Y extends X implements I{}

X obj=new Y();

I obj=new Y();

X is-a Y

X is a I

X is a Object

Refer this concept : Since Object is the father class of all classes in Java , So we can say X is a Object.

Runtime Polymorphism Example in Java.

Here in this example we have created a class Sport with a method name as myMethod()that printing just a text as In Sport Class, then we have created a class cricket which extends Sport class and override the myMethod() method of Sport Class and providing implementation according to our requirement, after that we have created a class Football which also extends Sport and providing implementation according to requirement.

Now we have created a class Testmain with main method and we are calling myMethod() by the reference variable of parent class i.e., Sport class. Since it refers to the child class objects and child class overrides the parent class(Sport class) method i.e., myMethod() and child class method is invoked at run time.

NOTE : Method to be called/invoked is determined by the JVM not by the compiler because compiler checks only reference type, it is known as runtime polymorphism.

class Sport{

void myMethod(){

System.out.println("In Sport Class");

}//end of method

}//end of classs

class Cricket extends Sport{

void myMethod (){

System.out.println("Playing Cricket");

}//end of method

}//end of classs

class Football extends Sport{

void myMethod (){

System.out.println("Playing Football");

}//end of method

}//end of class

public class Testmain {

public static void main(String[] args){

Sport s;

s=new Cricket();

s. myMethod();

s=new Football();

s. myMethod();

}

}
output:
Playing Cricket
Playing Football

Java Polymorphism Example With Bank.

Here we have created a class Bank similar to previous example of Sport class with respect to logic, here classes BOI, CanraBank and BOB extending Bank and providing specific implementation according to different requirement i.e., different Rate of Interest.

Now we have created a class Testmain with main method and we are calling getROI () by the reference variable of parent class i.e., Bank class. Since it refers to the child class objects and child class overrides the parent class (Bank class) method i.e., getROI () and child class method is invoked at run time, see example and try to understand.

class Bank{

float getROI(){return 0;}

}

class BOI extends Bank{

float getROI(){return 8.4f;}

}

class CanaraBank extends Bank{

float getROI(){return 7.3f;}

}

class BOB extends Bank{

float getROI(){return 9.7f;}

}

public class Testmain {

public static void main(String[] args){

Bank b;

b=new BOI();

System.out.println("BOI Rate of Interest: "+b. getROI());

b=new CanaraBank();

System.out.println("Canara Bank Rate of Interest: "+b. getROI());

b=new BOB();

System.out.println("BOB Rate of Interest: "+b. getROI());

}

}

output:
BOI Rate of Interest: 8.4
CanaraBank Rate of Interest:7.3
BOB Rate of Interest:9.7

Hope it was helpful.

You should know also.
What is inheritance in Java?

Java LinkedList Class

2018-11-18T09:31:00.004+05:30

Java LinkedList Class | What is LinkedList Class in Java Collecton?

Hello Readers in this article we are going to learn about JAVA

Collection LinkedList Class.

LinkedList Class in JAVA Collection is a Class which can be used to hold heterogeneous types of elements as Array allowed only homogeneous type of elements and it is fixed in size.

To overcome these problem we should go for Java Collection who provide several classes.Here we are looking for LinkedList Class.

Declaration/Hierarchy of Java Collection LinkedList Class.

public class LinkedList<E> extends AbstractSequentialList<E>

implements List<E>, Deque<E>, Cloneable, java.io.Serializable

LinkedList Class

The underlying data structure is doubly linked list.

It uses doubly linked list to store the elements.

In doubly Linked List case we add or remove elements from both side.

Insertion order is preserved.

It allows duplicate elements to be stored.

It allows null also.

It is not implements Random Access.

It better for to perform manipulation in between.

It is not recommended to perform retrieval operations.

Capacity concept not applicable in the case of LinkedList.

Java LinkedList Class is not Synchronized.

LinkedList extends AbstractSequentialList<E>implements List<E>, Deque<E>, Cloneable, java.io.Serializable.

Constructors of LinkedList Class.

1.LinkedList();

It creates an empty LinkedList.

2.LinkedList(Collection c);

It is used to creates an equivalent LinkedList object for the

given or specified Collection.

Method's

boolean add(Object o)

It is used to add the specified element to the end of a list.

void add(int index, Object element)

It is used to add the elements at the specified index in list.

void addFirst(Object o)

It is used to add element at the starting of a list.

void addLast(Object o)

It is used to add the element to the end of a list.

Object getFirst()

It is used to return the first element from a list.

Object getLast()

It is used to return the last element from a list.

boolean contains(Object o)

It is used to return true if the list contains the given element.

boolean remove(Object o)

It is used to remove the first occurrence of the specified element from a list.

int indexOf(Object o)

It is used to returns the index from a list of the first occurrence of the given element, it will return -1 if the list does not contain given element.

int lastIndexOf(Object o)

It is used to return the index in a list of the last occurrence of the given element, or it will return -1 if the list does not contain given element.

int size()

It is used to return the size/number of elements present in a list.

Java LinkedList Examples

In this example we will learn.

How to add elements in LinkedList?

How to print the elements of LinkedList?

How to get first element?

How to get last element?

How to get size of LinkedList?

How to get first occurrence of elements?

How to get last occurrence of elements?

How to check this list contains specific element?

How to remove elements?

How to remove first element from LinkedList?

How to remove last element LinkedList?

How to add elements of LinkedList to another LinkedList using addAll(Collection c) method?

How to add element at first index in LinkedList using addFirst() method?

How to add element at last index in LinkedList using addLast() method?

How to get elements of LinkedList one by one?

import java.util.*;

public class TestLinkedList{

public static void main(String[] args){

LinkedList<String> ll=new LinkedList<String>();

ll.add("Matin");

ll.add("Kishan");

ll.add("Dilshad");

ll.add("Manish");

ll.add("Chandan");

ll.add("Matin");

System.out.println("Normal Linked List");

System.out.println(ll);

System.out.println("Getting 1st Eement");

System.out.println(ll.getFirst());

System.out.println("Getting last Eement");

System.out.println(ll.getLast());

System.out.println("Size of list "+ll.size());

System.out.println("First Occurrence of Matin "+ll.indexOf("Matin"));

System.out.println("Lasst Occurrence of Matin "+ll.lastIndexOf("Matin"));

System.out.println("Is this list contains Kishan "+ll.contains("Kishan"));

System.out.println("Is list contains Kunal "+ll.contains("kunal"));

ll.remove("Manish");//removing manish

System.out.println(ll);

ll.removeFirst();//removing first element

System.out.println(ll);

ll.removeLast();//removing last element

System.out.println(“After removeFirst() and removeLast() ”+ll);

LinkedList<String> ls=new LinkedList<>();

ls.add("Cricket");

ls.add("FootBall");

ll.addAll(ls);//adding ls to ll at the end of ll

ll.addFirst("First Element");//adding to first in ll

ll.addLast("Last Element");");//adding to lasst in ll

System.out.println("After Addition of ls now Normal Linked List "+ll);

//Getting List elements one by one

System.out.println("Getting List Elements one by one");

for(String s:ll){

System.out.println(s);

}

}//end of main

}//end of class

output:

Normal Linked List

[Matin, Kishan, Dilshad, Manish, Chandan, Matin]

Getting 1st Eement

Matin

Getting last Eement

Matin

Size of list 6

First Occurrence of Matin 0

Lasst Occurrence of Matin 5

Is this list contains Kishan true

Is list contains Kunal false

[Matin, Kishan, Dilshad, Chandan, Matin]

[Kishan, Dilshad, Chandan, Matin]

After removeFirst() and removeLast()[Kishan, Dilshad, Chandan]

After Addition of ls now Normal Linked List [First Element, Kishan, Dilshad, Chandan, Cricket, FootBall, Last Element]

Getting List Elements one by one

First Element

Kishan

Dilshad

Chandan

Cricket

FootBall

Last Element

Java SportsLinkedList Examples

In this example we will see how to add user defined class object into LinkedList, first we have created a class named as SportLinkedList with id,sportname and city name and a parameterized constructor.

We have overridden a toString() method fot textual representation of object.After that we have created the object of SportLinkedList class by passing the required arguments and added then to LinkedList using add() method and displaying them.

import java.util.*;

public class SportLinkedList {

int id;

String sportname,cityname;

public SportLinkedList(int id, String sportname, String cityname) {

this.id = id;

this.sportname= sportname;

this.cityname= cityname;

}

@Override

public String toString() {

return id + "," + sportname + "," + cityname;

}

//Main Method

public static void main(String[] args) {

SportLinkedList sll1=new SportLinkedList(1, "Cricket", "Mumbai");

SportLinkedList sll2=new SportLinkedList(2, "FootBall", "Assam");

SportLinkedList sll3=new SportLinkedList(3, "Hockey", "Punjab");

LinkedList<SportLinkedList> ll=new LinkedList<SportLinkedList>();

ll.add(sll1);

ll.add(sll2);

ll.add(sll3);

System.out.println("id Sport City");

for(SportLinkedList ss:ll) { System.out.println(ss); }

}//End of main

}//End of class

Output:

id Sport City 1,Cricket,Mumbai2,FootBall,Assam 3,Hockey,Punjab

Hope it was helpful

If you want to become a leader then you should be a good reader.

See also

-Java Collection ArrayList class?

-What is the difference between ArrayList and LinkedList?

PHP Complete Login System With Session Using MySql Database

2018-11-06T23:05:00.001+05:30

PHP Complete Login System With Session Using MySql Database | PHP Session Login System.
Hello Readers...
-In this article we are going to create a login system with SESSION using HTML and PHP with MySql Database.

-First create a separate config.php file to create(configure) the connection with MySql Database.

-If we create a config.php file separately then we can use this file in all PHP pages where connection is required i.e.,we can reuse this file n number of times for Database Connection Purpose.
-Now create a login.php file this file is responsible to authenticate the user's credentials.
-Next create a welcome.php file if user successfully logged in then login.php will redirect the user from login to welcome page.
-Now create a logout.php file to destroy the session, so user's can be logged out.
-Assume our Database name is mysql@123 and Table name is login with username and password column.

So lets create config.php.
This file is responsible to establish the connection with Database.
config.php

<?php

/* Assume we are running MySQL with default setting (user 'root' with no password) */

define('DB_SERVER', 'localhost');

define('DB_USERNAME', 'root');

define('DB_PASSWORD', '');

define('DB_NAME', 'mysql@123');

/* Attempting to connect to MySQL database */

$con = mysqli_connect(DB_SERVER, DB_USERNAME, DB_PASSWORD, DB_NAME);

// Checking connection

if($con === false){

die("ERROR: Could not connect. " . mysqli_connect_error());

}

Now create a login.php file.
In login page we have created a form with two text-field i.e., username and password and a submit button to submit the form.

When user hit the submit button then this form has to perform the action on submitted data, here action file is login.php only means login form calling self login.php.

This login.php is is responsible to authenticate the users credentials and redirect them to welcome page.

This login.php is also checking if user is already logged in means session is not destroyed then this page will redirect the user directly to welcome page.
Here we are going to write PHP login logic inside login.php only.
login.php

<?php

session_start();

if(isset($_SESSION['username'])) //If user is already logged in //then

{ echo "

alert('If u want to login again then logout first!');

window.location='welcome.php';

</script>";

}

if($_SERVER["REQUEST_METHOD"] == "POST")

{

$username=$_POST['username'];

$password=$_POST['password'];

include('config.php');

$sql_query = "select count(*) as cntUser from login where username='".$username."' and password='".$password."'";

$result = mysqli_query($con,$sql_query);

$row = mysqli_fetch_array($result);

$count = $row['cntUser'];

if($count > 0){

$_SESSION['username'] = $username;

echo "<script>

alert('Success...');

function redi(){window.location='welcome.php';}

var msg='Please Wait While Redirecting To Welcome Page...';

document.write('<font color=blue>'+'please wait while redirecting to Welcome page...'+'</font>');

setTimeout('redi()',3000);

</script>";

}

else{

echo "

</script>";

}

<html>

<head>

<title>Login Page</title>

</head>

<body>

Username :<input type="text" name="username" id="username"/><br/>

Password :<input type="password" name="password" id="password"/><br/>

</form>

</center>

</body>

</html>

Now create welcome.php.
If user enter valid username and password then user will be redirected to this welcome.php,if user is not logged in and users want to access this page directly using url bar then it will send the user back to login page.See below example...
welcome.php

<?php

session_start();

$username = $_SESSION['username']; //retrieve the session value

if(!isset($_SESSION['username'])) //If user is not logged in then //he cannot //access the welcome page

{

echo "

window.location='login.php';

</script>";

}

<html>

<head>

<title>

Welcome Page

</title>

</head>

Welcome User <?php echo $username;?>.<br/>

<a href="logout.php">Logout?</a>

</center>

</body>

</html>

Now create a logout.php file so user's can be logged out.
When user's click on logout button or link that is present on welcome page then this logout.php will be responsible to perform logout operation.
logout.php

<?php

session_start();

$username = $_SESSION['username']; //retrieve the session variable

unset($_SESSION['username']); //to remove session variable

session_destroy(); //destroy the session

<html>

<head>

<title>Logout Page</title>

</head>

<body>

<h4>Your are logged out<h4>

<h4><a href="login.php">Login Again?<a></h4>

</center>

</body>

</html>

Hope it was helpful.

See also-Basic Php Login System

Php Login System With Mysql Database

2018-11-05T16:27:00.003+05:30

PHP Login System With MySql Database | PHP Login System.

Hello Readers...

In this article we are going to create a login system using HTML and PHP.

-First create a separate config.php file to create the connection with MySql Database.

-If we create a config.php file separately then we can use this file in all PHP pages where connection is required i.e.,we can reuse this file n number of times for Database Connection Purpose.

-Now create login.php file,this file will be responsible to to authenticate the users credentials and redirect then to welcome page.

-Assume our Database name is mysql@123 and Table name is login with username and password column.

So lets create config.php.

This file is responsible to establish the connection with MySql Database.

config.php

<?php

/* Assume we are running MySQL with default setting (user 'root' with no password) */

define('DB_SERVER', 'localhost');

define('DB_USERNAME', 'root');

define('DB_PASSWORD', '');

define('DB_NAME', 'mysql@123');

/* Attempting to connect to MySQL database */

$con = mysqli_connect(DB_SERVER, DB_USERNAME, DB_PASSWORD, DB_NAME);

// Checking connection

if($con === false){

die("ERROR: Could not connect. " . mysqli_connect_error());

}

Now create a login.php file.

Here we are going to write PHP login logic inside login.php only.

In this file we have created a form with two text-field i.e., username and password to take input from the user's.

We have also created a submit button to submit the form after filling username and password.

When user hit the submit button after filling username and password then this login.php is responsible to authenticate the user credentials.

If user enter valid username and password then user will be redirected to welcome page otherwise a message will be displayed saying invalid login details,see below example.

login.php

<?php

if($_SERVER["REQUEST_METHOD"] == "POST"){

$username=$_POST['username'];

$password=$_POST['password'];

include('config.php');

$sql_query = "select count(*) as cntUser from login where username='".$username."' and password='".$password."'";

$result = mysqli_query($con,$sql_query);

$row = mysqli_fetch_array($result);

$count = $row['cntUser'];

if($count > 0){

echo "

alert('Success...');

function redi(){window.location='welcome.php';}

document.write('<font color=blue>'+'please wait while redirecting to Welcome page...'+'</font>');

setTimeout('redi()',3000);

</script>";

}

else{

echo "

</script>";

}

<html>

<head>

<title>Login Page</title>

</head>

<body>

Username :<input type="text" name="username" id="username" required="required"/><br/>

Password :<input type="password" name="password" id="password" required="required"/><br/>

</form>

</center>

</body>

</html>

Now create welcome.php.

If user entered valid username and password then login page will redirect the user's to this welcome.php

welcome.php

<html>

<head>

<title>

Welcome Page

</title>

</head>

Welcome User to our Welcome Page.

</center>

</body>

</html>

Hope this article was helpful.

Java Generics Object Behavior in Non Generic Area

2018-10-29T17:49:00.002+05:30

Java Generic Objects Behavior in Non Generic Area | Generic Class | Generic Methods.
Hello Java Lovers in this article we are going to see Java Generic objects behavior in Non-Generic area, and Java Non-Generic object behavior in Java Generic area.

So lets begin...

First See This Example Of ArrayList With Non-Generic Concept And Try To Understand Problem With This Example.

Example of Java Non-Generic ArrayList.
import java.util.*;
public class MyClass{
public static void main(String args[]){
ArrayList al=new ArrayList();
al.add("Matin");
al.add("Sharavan");
al.add(10);
System.out.println(al);
String s=(String)al.get(2);
System.out.println(s);
}
}
output:
[Matin,Shravan,10]
Exception in thread "main" java.lang.ClassCastException: java.lang.Integer cannot be cast to java.lang.String
at com.JavaTpoint.TestMain.main(MyClass.java:line no)
-So in the above example we added two String and one Integer elements to ArrayList,after that we are printing the elements present inside ArrayList Ok.
-After that we used get() method to get 2nd index element,but here we don't know the type of elements,we are holding 2nd index element in String then we will get compile time error but after Type Casting error will be resolved but at run time we will get Class Cast Exception.

-So in the above example Type Safety and Type Casting problem raised,to resolve these problems SUN People came with Generic Concept.See below example...

Now Example of Java Generic ArrayList.

import java.util.*;
public class MyClass{
public static void main(String args[]){
ArrayList<String> al=new ArrayList<String>();
al.add("Matin");
al.add("Sharavan");
al.add("Sagar");
//al.add(10);//compile time error
System.out.println(al);
String s=al.get(2);
System.out.println(s);
}//end of main
}//end of class

output:
[Matin,Shravan,Sagar]
Sagar

-Now here we can add only String type of elements,so we can give the guarantee the Type of Elements present inside ArrayList.
-So Here Type Casting is not required because we know the type of elements.
-Achieved Type Safety.
-Compile time checking,See line number 8,at line number 8 i am trying to add Integer element then immediately we are getting compile time error saying,The method add(int, String) in the type ArrayList<String> is not applicable for the arguments (int).
-Compile time error is better than Run Time.

Now Java Generic Object Behavior in Non-Generic Method/Area.
Consider the example given below,read it carefully.
Real Life Example:
-One day in morning i went to my friends home (he is pure vegetarian) to discuss something,while discussing i asked him do you eat Non-Veg,then in front of his parent he said no no how i can eat Non-Veg as i am vegetarian.

-After sometime me and my friend came back to my home,i am Non-Vegetarian,I took a plate and served chicken and i start eating my friend is also there with me,he asked me hey what you are eating then i told this is chicken,suddenly in middle my friend took one piece of chicken and start eating,then i asked him oye you are vegetarian then how you can eat chicken then he told usually i eats Non-Veg's then i asked him but in the morning when i asked do you eat Non-Veg's then you said no no i am vegetarian then he said no no i also eat Non-Veg's too but when i am outside from my home.

-Again in the evening i went to my same friend's home to play chess then at that time intentionally i asked him do you eat Non-Veg's,again he told no no i am pure vegetarian how i can eat Non-Veg's in front of his parent's ;).
-So here my friend is vegetarian at his home in front of his parent's.
But outside he can eat Non-Veg's too,means he is changing his behavior accordingly.

Now see below practical example...
import java.util.*;
public class MyClass{
public static void myFriendatMyHome(ArrayList myfriends) {
myfriends.add(1);
myfriends.add(4.1f);
myfriends.add(66.45);
myfriends.add("Chicken");
}
public static void main(String[] args){
ArrayList <String> myFriendatHishome=new ArrayList <String>();
myFriendatHishome.add("Patato");
myFriendatHishome.add("Tomato");
myFriendatHishome.add("Onion");
//myFriendatHishome.add(1);//Compile time error
//Consider 1 as chicken
System.out.println("My Friend can eat/add only "+myFriendatHishome+" at his home in front of his parent's");

myFriendatMyHome(myFriendatHishome);
//passing Generic ArrayList Object to Non-Generic Area/Method
System.out.println("But At My Home he can eat/add "+myFriendatHishome+" also");
}
}
Output:
My Friend can eat/add only [Patato, Tomato, Onion] at his home in front of his parent's

But At My Home he can eat/add [Patato, Tomato, Onion, 1, 4.1, 66.45, Chicken] also.
-So from the above example myFriendatHishome he can eat/add only vegetables but after coming at myFriendatMyHome(myFriendatHishome); he can eat/add Chicken/Mutton etc.
-Means behavior of My Friend changing accordingly.
-Communication of Generic Code with Non-Generic Code.
-When we passed Generic ArrayLsit object myFriendatHishome to Non-Generic Area/Method myFriendatMyHome(myFriendatHishome) then My Friend i.e. myFriendatHishome behaving like Non-Generic i.e.(Behavior from Vegetarian to Non-Vegetarian).

Similarly a Non-Generic Object in will behave like Generic in Generic Method/Area.

Consider Below Example...

import java.util.*;
public class MyClass{
public static void genericArea(ArrayList<String> generic) {
generic.add("Virat");
generic.add("Rohit");
generic.add("Cricket");
//generic.add(1);//Compile Time Error
}
public static void main(String[] args){
ArrayList nonGeneric=new ArrayList();
nonGeneric.add(1);
nonGeneric.add("Tomato");
nonGeneric.add(66.45);
nonGeneric.add(5.6f);
System.out.println("Non-Generic "+nonGeneric);
genericArea(nonGeneric); //passing generic object to non generic //area genericArea(nonGeneric)

System.out.println("After passing non generic obj to generic area/method "+nonGeneric);
}//end of main
}//end of class
Output:
Non-Generic [1, Tomato, 66.45, 5.6]
After passing non generic obj to generic area/method [1, Tomato, 66.45, 5.6, Virat, Rohit, Cricket]

In the above example we are passing a non generic object
nonGeneric to generic method/area,so the behavior of non generic obj will be changed to generic behavior.

Java ArrayList With Simple Example

2018-10-27T15:47:00.000+05:30

Java ArrayList With Simple Example | Java ArrayList

In Java ArrayList is a class which is used to store elements.
It inherits AbstractList Class which implements List interface.

Points to remember about Java ArrayList Class.

It is re-sizeable /grow-able Array also called as Dynamic Array.
It allows duplicate elements.
It can contain null also.
It maintain the insertion order i.e., insertion order is preserved.
Heterogeneous objects are allowed.
It is best for search operations.
It implements Random access hence it is best for search operations.
In ArrayList Manipulation is slow because lot of shifting is required if any elements is removed from it.

ArrayList Class

As shown in the diagram it extends AbstractList class which implements the List interface, and List interface extends the Collection and Iterable interface.

Declaration of ArrayList Class.

It is present in java.util package.
public class ArrayList<E> extends AbstractList<E> implements List<E>,RandomAccess,Cloneable,Serializable.

Constructors of ArrayList

1.ArrayList();

It creates an empty ArrayList with initial capacity i.e.10.
When ArrayList reached its max capacity then it creates a new ArrayList with 50% increment in initial capacity.
New Capacity=(Current Capacity x3/2)+1;

2.ArrayList(int Initial capacity);

It creates an ArrayList with specified initial capacity.

3.ArrayList(Collection);

It creates an equivalent ArrayList object for given collection.

Now Java ArrayList Method

There are following methods:
void add(Object obj);
-Used to add elements to end of an ArrayList.
void add(int index,Object obj);
-Used to add elements to specified index in a ArrayList.
boolean addAll(Collection c);
-Used to add elements of specified collection to the end of an ArrayList.
boolean addAll(int index,Collection c);
-Used to add elements of specified collection to an ArrayList from the specified index of an ArrayList.
void clear();
-Used to remove all elements from an ArrayList.
int indexOf(Objec obj);
-Used to return the first index of specified element as it allows duplicates.
int latIndexOf(Objec obj);
-Used to return the last index of specified element as it allows duplicates.
Object[] toArray();
-Used to return an array of current ArrayList in correct order.
Object clone();
-Return a shallow copy ArrayList.
void trimToSize();
Used to trim the capacity of this ArrayList instance to be the current size.

Creating an ArrayList and adding new Elements to it.

This example shows:

How to create an ArrayList using ArrayList() constructor.
Adding new elements to an ArrayList using add() method.
Adding new elements at specified index to an ArrayList using add(int index) method.

import java.util.*;
public class ArrayListExample {
public static void main(String[] args) {
List al=new ArrayList();
al.add(1);
al.add(2);
al.add(3);
System.out.println(al);
//adding an elements to arraylist with specified index
al.add(0,100);
System.out.println(al);
}
}
output:
[1, 2, 3]
[100, 1, 2, 3]

How to create an ArrayList from another Collection?
In this example we are going to see:

How to create an ArrayList from another Collection using ArrayList(Collection c) constructor.
How to add all elements from existing collection to new ArrayList using addAll() method.

import java.util.*;

public class ArrayListExample2 {

public static void main(String[] args) {

List<Integer> firstFiveNumbers=new ArrayList<Integer>();

firstFiveNumbers.add(1);

firstFiveNumbers.add(2);
firstFiveNumbers.add(3);

firstFiveNumbers.add(4);

firstFiveNumbers.add(5);

List<Integer> firstTenNumbers=new ArrayList<Integer> (firstFiveNumbers);

List<Integer> nextFiveNumbers=new ArrayList<Integer>();

nextFiveNumbers.add(6);

nextFiveNumbers.add(7);

nextFiveNumbers.add(8);

nextFiveNumbers.add(9);

nextFiveNumbers.add(10);

//adding all elements of nextFiveNumbers to firstTenNumbers

firstTenNumbers.addAll(nextFiveNumbers);

System.out.println(firstTenNumbers);

}

output:

[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

Non Generic vs Generic ArrayList.

Programmers can ad any type of objects to the ArrayList but at run time suppose if we added Integer to ArrayList and if we try to get 0th index element using get(0) method then what is the type of 0th element we don't know and we are trying to hold it in String then compile time error occured but if we perform Type Casting then error will solve but at run time we will get ClassCastException.
See Example...
1.Non Generics
import java.util.*;
public class ArrayListDemo{
public static void main(String args[]){
List li=new ArrayList();
li.add("one");
li.add(1);
String s=(String ) li.get(1);
System.out.println(s);
}
}
output:
Exception in thread "main"
java.lang.ClassCastException: java.lang.Integer cannot be cast to java.lang.String
-So Here Type Safety and Type Casting Issue raised in the above example.
To overcome these problem SUN People come with Generic Version of ArrayList.
2.Generic ArrayList

import java.util.*;
public class ArrayListDemo2{
public static void main(String args[]){
List<String> li=new ArrayList<String>();
li.add("one");
li.add("two");
String s=li.get(1);
System.out.println(s);
}
}
output:two

In the above example we have created Generic List with angular braces<String>,So we can add String object only to this list, If we try to insert any other type of object then we will get compile time error.
So after generic version of ArrayList we can store specific type of elements in Collection.
So Type Safety and Type Casting Problem is resolved.
Compile time checking because Compile Time Checking is better than Run Time.

How to access elements of an ArrayList?
see the example...
import java.util.*;
public class MyClass{
public static void println(String args[]){
List<String> players=new ArrayList<String>();
System.out.println("Is the Players list empty? yes it is "+players.isEmpty());
players.add("Matin");
players.add("Vijay");
players.add("Manish");
players.add("Praksh");
players.add("Shravan");
//Size of players list
System.out.println("Here is the Top "+players.size()+" Players List");
System.out.println(players);
//Retrieving the players from list see below
System.out.println("No One Player "+players.get(0));
System.out.println("No Two Player "+players.get(1));
System.out.println("Last Player in the list is "+players.get(players.size()-1));
//Now changing the No One Players i.e Modification
players.set(0,"Akash");
System.out.println("Now No One Player in the list is "+players.get(0));
System.out.println(players);
}
}
output:
Is the Players list empty? yes it is true
Here is the Top 5 Players List
[Matin, Vijay, Manish, Praksh, Shravan]
No One Player Matin
No Two Player Vijay
Last Player in the list is Shravan
Now No One Player in the list is Akash
[Akash, Vijay, Manish, Praksh, Shravan]
So from the above example we learnt.

How to check either ArrayList is Empty or not using isEmpty() method.
How to check the size of an ArrayList using size() method.
How to access an element at particular index in an ArrayList using get(int index ) method.
How to change an element at particular index in an ArrayList using set(int index,String element) method.

HOW TO REMOVE ELEMENTS FROM AN ArrayList?
In this example we are going to see how to remove an elements from an ArrayList using/
remove(Object obj).
remove(int index).
removeAll(Collection<?> c).
removeIf().
remove().
File Name:
MyRemovingClass.java
import java.util.*;
import java.util.function.Predicate;
public class MyRemovingClass{
public static void main(String args[]){
List<String> players=new ArrayList<String>();
players.add("Matin");
players.add("Vijay");
players.add("Manish");
players.add("Praksh");
players.add("Shravan");
System.out.println("Top 5 Players List at initial Stage "+players);

//removing element using remove(Objec obj)
//remove(Objec obj) return false if element does not exist
boolean b=players.remove("Shravan");
System.out.println(b);
System.out.println("After Removal of Shravan "+players);

//removing element using remove(int index),
//it remove the element of specified index and return that element
String removedElement=players.remove(3);
System.out.println("Removed Element "+removedElement);

//Now Stable ArrayLsit
System.out.println("Now Players List After remove(3) "+players);

// satisfying the given predicate and removing elements
players.removeIf(new Predicate<String>() {
@Override
public boolean test(String element) {
return element.endsWith("n");
}
});
System.out.println("After removing elements ends with n, Now Remaining Players "+players);

//removing all elements from an arraylist using clear() method
players.clear();
System.out.println("After clear() "+players);
}
}
output:
Top 5 Players List at initial Stage [Matin, Vijay, Manish, Praksh, Shravan]
true
After Removal of Shravan [Matin, Vijay, Manish, Praksh]
Removed Element Praksh
Now Players List After remove(3) [Matin, Vijay, Manish]
After removing elements ends with n, Now Remaing Players [Vijay, Manish]
After clear() []

Iterating over an ArrayList

File Name:
IteratingClass.java
import java.util.*;
public class IteratingClass{
public static void main(String args[]){
List<String> players=new ArrayList<String>();
players.add("Matin");
players.add("Vijay");
players.add("Manish");
players.add("Praksh");
players.add("Shravan");
System.out.println("Before Iteration "+players);
//Iterating using for loop
System.out.println("After Iteration Using Normal For Loop");
for(int i=0;i<players.size();i++)
{
System.out.println(players.get(i));}
}
System.out.println("=======================");
//Iterating using for each loop
System.out.println("After Iteration using For Each ");
for(String player:players)
{
System.out.println(player);
}
System.out.println("=======================");
//Iterating using Iterator
System.out.println("Iterating using Iterator ");
Iterator<String> itr=players.iterator();
while(itr.hasNext())
{
System.out.println(itr.next());
}
System.out.println("=======================");
//Iterating in backward direction using ListIterator
System.out.println("Iterating in backward direction using ListIterator ");
ListIterator<String> itr=players.listIterator(players.size());
while(itr.hasPrevious())
{
System.out.println(itr.previous());
}
System.out.println("=======================");
//Iterating in backward direction using ListIterator
System.out.println("Iterating in backward direction using ListIterator ");
ListIterator<String> itr=players.listIterator();
while(itr.hasNext())
{
System.out.println(itr.next());
}
System.out.println("=======================");

//Iterating using Java 8 forEach and lambda
System.out.println("Iterating using Java 8 forEach and lambda ");
players.forEach(play -> {
System.out.println(play);
});
System.out.println("=======================");
}//end of main
}//end of class

OutPut:
Before Iteration [Matin, Vijay, Manish, Praksh, Shravan]
After Iteration Using Normal For Loop
Matin
Vijay
Manish
Praksh
Shravan
====================

After Iteration using For Each

Matin

Vijay

Manish

Praksh

Shravan

=======================

Iterating using Iterator

Matin

Vijay

Manish

Praksh

Shravan

=======================

Iterating in backward direction using ListIterator

Shravan

Praksh

Manish

Vijay

Matin

=======================

Iterating in forward direction using ListIterator

Matin

Vijay

Manish

Praksh

Shravan

=======================

Iterating using Java 8 forEach and lambda
Matin
Vijay
Manish
Praksh
Shravan
=======================

List and ListIterator
Iterator

It can traverse the elements in forward direction only.
This Iterator can be used with List,Set and Queue.
While traversing the element it can perform remove operation only.

whereas...

ListIterator

It can traverse the element in both direction i.e. Forward as well as Backward.
This Iterator can be used with List only.
While traversing the elements it can perform add,remove and set operations.

Hope This Article Was Helpful.

You should know also.
Difference between ArrayList and LinkedList

Inheritance in java

2018-10-25T13:06:00.000+05:30

What is Inheritance in Java?
Inheritance in Java is a technique/mechanism in which child class object can acquires all the properties and behavior of parent class object.It is an important part of OOP's concept in Java.

The purpose behind inheritance concept in Java is that we can create a new classes that are built upon existing classes.When we inherit(extends) from an existing class,we can reuse methods and fields of the parent class.

Note:We can add new methods and fields in our current class,we can develop our current class according to our requirement,no restrictions.

In JAVA Inheritance represents the IS-A relationship concept which is also known as parent-child relationship.

Why Inheritance in Java

If you want to override a method then Inheritance is the first requirement.
Code Reusabiltiy.

Components of Inheritance
Class: A class is a blueprint from objects are created.
Child Class/Sub Class: Sub OR Child class is a class which inhertis/extends the other class.It is also known as derived class.
Parent/Super Class : Super OR Parent class is a class from where a child class inhertis the features.It is also known as Base Class.
Reusability: As the name says, reusabilty is a technique which allow us to reuse the fields and methods of an existing class when we creates a new classes. We can use the same fields and methods that is already defined in the parent class.

Standard Syntax of Java Inheritance

class Child/Sub_Class-Name extends Parent/Super_Class-Name

{

//methods and fields Depend on requirement

}

The extends keyword ensures that we are creating a new class that derives from an existing class.The meaning of extends keyword is to increase the functionality.
In other words a class which is inherited is known as Parent/Base Class,and a new class which is inheriting the properties of Base/Parent Class known as child class.

Java Inheritance Example
class Sport{
String sportName="CRICKET";
}
public class Mumbai extends Sport{
String msg="Mumbaikar's Best Sport is ";

public static void main(String args[]){
Mumbai m=new Mumbai();
System.out.println(m.msg+m.sportName);
}
}
output:
Mumbaikar's Best Sport is CRICKET
Note: In the above example Mumbai Class object can access it's own field i.e. msg as well as other class field i.e. sportName of Sport class i.e., Code Reusability.

Types of inheritance in Java

Note: Multiple Inheritance not supported in Java through Class.When one class inherits multiple classes known as Multiple inheritance.

Single Inheritance Example
File Name: TestMain.java
class Sport{
String sportName="CRICKET";
}
class Mumbai extends Sport{
String msg1="Mumbaikar's Best Sport is ";
}
public class TestMain{
    public static void main(String args[]){
  Mumbai m=new Mumbai();
    System.out.println(m.msg1+m.sportName);
}
}
output:
Mumbaikar's Best Sport is CRICKET

Multilevel Inheritance Example
File Name: TestMain2.java
class Sport{
String sportName="CRICKET";
}
class Mumbai extends Sport{
String msg1="Mumbaikar's Best Sport is ";
}
class Delhi extends Mumbai{
String msg2="Best sport of Delhi is ";
}
public class TestMain2{
   public static void main(String args[])
{
  Delhi d=new Delhi();
    System.out.println(d.msg2+d.sportName);
}
}
output:
Best sport of Delhi is CRICKET

Hierarchical Inheritance Example
File Name: TestMain3.java
class Sport{
String sportName="CRICKET";
}
class Mumbai extends Sport{
String msg1="Mumbaikar's Best Sport is ";
}
class Delhi extends Sport{
String msg2="Best sport of Delhi is ";
}
public class TestMain3{
public static void main(String args[]){
Delhi d=new Delhi();
System.out.println(d.msg2+d.sportName);
//but now below trying to access msg1 of Mumbai Class
//System.out.println(d.msg1);//compile time error:msg1 can not be resolved or is not a field
}
}
output:
Best sport of Delhi is CRICKET

Multiple Inheritance Example
Multiple Inheritance not supported in Java!Why?

To simplify and to reduce the complexity Multiple Inheritance not supported in Java.

Consider the below example,we have three classes i.e., Mumbai,Delhi and TestMain4 with main method. And Mumbai and Delhi both have same msg() method.Here TestMain4 extends Mumbai and Delhi, and if we try to call msg() method using the object of child class i.e. TestMain4 then there will be ambiguity to call the msg() method of Mumbai OR Delhi.

Since compile time error is better than run time error. So whether we have same or different method there will be compile time error if you try to extending two classes.see below example...

File Name: TestMain4.java
class Mumbai  {
void msg(){
System.out.println("Playing Cricket");
}
}

class Delhi  {
void msg(){
System.out.println("Playing Cricket");
}
}

public class TestMain4 extends Mumbai,Delhi  {
   public static void main(String args[]){
  TestMain4 obj=new TestMain4();
obj.msg();//Now here which msg() method would be invoked
}
}
output :compile time error

Hope This Article Was Helpful.

what is generics in java with simple example

2018-10-23T23:02:00.003+05:30

Generics in Java | What is Generics in Java
The Java Generics concept introduced in Java 5 to deal with type-safe objects.

Before Generics,programmers can store any type of objects in collection framework i.e., non-generics.

Now Java Generics forces programmers to store specific type of objects.

Objective of Java Generics

Type-Safety.
To Remove Type Casting Problem.

Type Safety

Arrays are type safe i.e. we can give guarantee for the type of element present inside array.

For example:

If programmer requirement is to hold only String type of object then we can choose String Array ,by mistake if we are trying to insert any other type of object then we will get compile time error saying Type Mismatch.

String [] s=new String[10];

s[0]="The Tech Matin";

s[1]=new Integer(1);//here we will get compile time error saying //Type Mismatch:can not convert from Integer to String

Hence String Array can contain only String Type of Objects,due to this we can say Arrays are Type Safe.

But Collection's are not Type Safe i.e. we can not give the guarantee for type of elements present inside Collection's.

Example:

If programmer requirement is to hold only String Type of Objects ,if we choose ArrayList and by mistake if we add any other type of objects then at that time we won't get any compile time error but the program will fail at Run Time.

ArrayList al=new ArrayList();
al.add("abc");
al.add(new Integer(1));
String s=(String)al.get(1);
System.out.println(s);

In the above example we are adding one String element and one Integer element.
After adding element to ArrayList we are trying to get the element of 1st index and trying to hold it in String,here at line number 4 we will get compile time error saying Type Mismatch:can not convert from Object to String,because we don't know the type object,hence we need to do Type Casting.
After type casting error will be resolved but at Run Time we will get Run Time Exception Saying :Exception in thread "main" java.lang.ClassCastException: java.lang.Integer cannot be cast to java.lang.String.

#To Overcome these problems SUN PEOPLE introduced Generic Concept in 1.5 Version.

Hence main objective of Java Generics are

To provide Type Safety.
To Resolve Type Casting Problem.

#To hold only String type of Objects we can create Generics Version of ArrayList as shown Below.

ArrayList<String> al=new ArrayList<String>();
al.add("abc");
al.add(new Integer(1));//

In the above ArrayList we can add only String Type of Objects,If we try to insert any other type of object then we will get Compile Time Error Saying At Line No. 3:The method add(String) in the type ArrayList<String> is not applicable for the arguments (Integer).

Hence through Generics we are getting Type Safety And Hence

String s=al.get(0);//No Type Casting

Type Casting Problem Also Resolved.

Full Example Of Generics In Java
public class GenDemo{
public static void main(String[] args) {
ArrayList<String> al=new ArrayList<String>();
al.add("The");
al.add("Tech");
al.add("Matin");
al.add(3);//comile time error
System.out.println(al.get(0)+" "+al.get(1)+" "+al.get(2));//No Type Casting Required :)
}//end of main
}//end of class

Main Advantage Of Java Generics

Type Safety
Type Casting is not required
Compile Time Checking

Example of Java Generics Using Map

public class GenDemo {

public static void main(String[] args) {

Map<Integer, String> map=new HashMap<Integer, String>();

map.put(1,"Matin");

map.put(2,"Vijay");

map.put(3,"Darshan");

Set<Map.Entry<Integer, String>> set=map.entrySet();

Iterator<Map.Entry<Integer, String>> itr=set.iterator();

while(itr.hasNext()){

Map.Entry<Integer, String> data=itr.next();

System.out.println(data.getKey()+" "+data.getValue());

}//end of while

}//end of main

}//end of class

Generic Class

A class that can refer to any type is known as Generic Class.
Here we are using T type parameter to create a Generic Class.
Let's see the example

Class TheTechMatin<T>{

T object;

void add(T object){

this.object=object;

}

T get(){

return object;

}

public static void main(String[] args) {

TheTechMatin<Integer> obj=new TheTechMatin<Integer>();

obj.add(3);

obj.add("Matin");//Compile Time Error

System.out.println(obj.get());

}//end of main

}//end of class

output: 3

Java Generics Type Parameters

The Type Parameter Naming Conventions are important to learn

Generics Thoroughly.

Common Type Parameter are as follows:

T-Type
E-Element
K-Key
N-Number
V-Value

Generic Method

Like Generic Class,we can create a Generic Method that can accept any type of argument.
Let's see the simple example of Java Generic Method

public class MyClass{

public static <E> void printMyArray(E[] element){

for(E elements:element){

System.out.println(elements);

}

System.out.println();

}

public static void main(String[] args) {

Integer[] i= {1,2,3,4};

System.out.println("Printing Integers");

printMyArray(i);

String [] s= {"one","Two","Three","Four"};

System.out.println("Printing String");

printMyArray(s);

}

}
O/P
======
Printing Integers
1
2
3
4
Printing String
one
Two
Three
Four

WildCard in Java Generics

In Java Generics ?(Question mark) represent the wildcard element.
It means any type.
If we write <? extends Number> then,it means either Number or its Child Class.Ex Integer,Float,Double etc.
Now we can call the methods of Number Class through any child class.

See example carefully for better understanding:
abstract class Alphabet
{
abstract void methodName();

}
class A extends Alphabet
{
@Override
void methodName() {
System.out.println("A Belongs To Alphabet");
}
}

class B extends Alphabet
{
@Override
void methodName() {
System.out.println("B Belongs To Alphabet");
}
}
public class MyClass{
public static void readAlphabets(List<? extends Alphabet> list){
for(Alphabet lists:list){
lists.methodName();
}
}
public static void main(String args[]){
List<A> list1=new ArrayList<A>();
A a=new A();
list1.add(a);

List<B> list2=new ArrayList<B>();
B b=new B();
list2.add(b);

readAlphabets(list1);
readAlphabets(list2);
}//end of main
}//end of class
Out/Put:
A Belongs To Alphabet
B Belongs To Alphabet

Hope This Article Was Helpul.

Performing Database Operations Java Sql Insert Update Delete Select

2018-10-12T15:43:00.000+05:30

Performing Database Operations in Java |SQL
INSERT,UPDATE,DELETE and SELECT.
This post is going to help you in learning how to do basic database operations using JDBC(Java Databse Connectivity) API.These basic operations are INSERT,UPDATE,SELECT and DELETE statements in SQL.Here we are going to use MySql DataBase.

Prerequisites:
-Eclipse IDE or Any
-JDK
-MySql Connector Jar File.

Creating Database:
-use the following statement
create database database_name;
Here i want my database name as thetechmatin;

so execute the following statement
create database thetechmatin;
That's all for Database Creation.

Now create a Table give name as users,execute the below statement.
create table users(Fname varchar(20),Lname varchar(20));

So now we have a database thetechmatin and a Table users with column Fname and Lname.
----------------------------
| Fname | Lname |
---------------------------
Now first we are going to perform INSERT Operation from java application.
-So a create project in Eclipse IDE,give any name for example JDBCOperations.
-Add MySql Connector Jar File.
-To add jar file to your project right click on project 1)now click on configure build path,2)click on Add External Jars,3)Nowfind your downloaded mysql connector jar file and double click on that jar file and say apply and close.

-Now Register the Driver Class.
To register the driver class use the below code
Class.forName("com.mysql.jdbc.Driver");

-Create the connection.
To create the connection with the Database use the below code
Use DriverManager Class Factory Method getConnection(); which returns the instance of Connection Interface.
Connection conn=DriverManager.getConnection("url","username","password");

-Create the statement.
-To create the statement use instance of Connection interface which you got in previous step,call createStatement() methos or PreparedStateemt() method using the conn instance.
conn.createStatement(); or conn.prepareStatement();//recommended
It will returns the instance of Statement OR PreparedStatement Interface,it will help us to execute the query using its factory methods i.e.,execute(),executeQuery(),executeUpdate() using these method we can get the instance of ResultSet Interface which will help us to get the data from the table.

See Below Example For Better UnderStanding
Now create a class give name as JDBCOperationsClass.

public class JDBCOperationsClass{
public static void main(String args[]){
try {
Class.forName("com.mysql.jdbc.Driver");
Connection conn=DriverManager.getConnection("jdbc:mysql://localhost:3306/tech matin","root","");
String query="INSERT INTO users('matin','mansoori') VALUES(Fname,Lname)"; PreparedStatement ps=conn.prepareStatement(query);
ps.executeUpdate();
System.out.println("Inserted");
ps.close();
conn.close();
}//end of try
catch(Exception exx){
System.out.print(exx.getMessage());
}//end of catch
}//end of main
}//end of class

NOW PERFORMING SELECT OPERATION TO FETCH RECORDS FROM TABLE.

public class JDBCOperationsClass{
public static void main(String args[]){
try{
//registering the driver class
Class.forName("com.mysql.jdbc.Driver");
//creating connection
Connection conn
=DriverManager.getConnection("jdbc:mysql://localhost:3306/thetechmatin","root","");
//writing query
String query="Select DISTINCT(Fname) from users";
PreparedStatement ps=conn.prepareStatement(query);
ResultSet rs=ps.executeQuery();
while(rs.next()){
String name=rs.getString("Fname");
System.out.println(name);
}//end of while
ps.close();
conn.close();
}//end of try
catch(Exception exx){
System.out.print(exx.getMessage());
}//end of catch
}//end of main
}//end of class

NOW PERFORMING UPDATE OPERATION TO UPDATE DATA INTABLE.

public class JDBCOperationsClass{
public static void main(String args[]){
try{
Class.forName("com.mysql.jdbc.Driver");
Connection conn
=DriverManager.getConnection("jdbc:mysql://localhost:3306/thetechmatin","root","");
String query="UPDATE users set Fname='Dilshad' where Fname='matin' ";
PreparedStatement ps=conn.prepareStatement(query);
ps.executeUpdate();
System.out.println("Updated");
ps.close();
conn.close();
}//end of try
catch(Exception exx){
System.out.print(exx.getMessage());
}//end of catch
}//end of main
}//end of class

NOW PERFORMING DELETE OPERATION TO DELETE ALL DATA FROM A TABLE.

public class JDBCOperationsClass{
public static void main(String args[]){
try{
Class.forName("com.mysql.jdbc.Driver");
Connection conn
=DriverManager.getConnection("jdbc:mysql://localhost:3306/thetechmatin","root","");
String query="DELETE * FROM users";
PreparedStatement ps=conn.prepareStatement(query);
ps.executeUpdate();
System.out.println("Deleted");
ps.close();
conn.close();
}//end of try
catch(Exception exx){
System.out.print(exx.getMessage());
}//end of catch
}//end of main
}//end of class

Hope this article will help you to understand basic SQL Database Operations using a JAVA Application.

Jsp Servlet Login And Logout System With Mysql Database

2018-10-11T17:58:00.003+05:30

JSP SERVLET LOGIN AND LOGOUT SYSTEM WITH MYSQL DATABASE.
Here we are going to create a complete login system using Jsp and Servlet.

Open Your Eclipse IDE

Create a dynamic web project in eclipse.

Add MySql connector jar file to your project.

Now in src directory create two servlet give name as Loginservlet.java and Logoutservlet.java.

Now in web-content directory create two jsp file give name as login.jsp and loginsuccess.jsp.

A web.xml(deployment descriptor) file will be created inside web-inf folder present inside web-content directory(Note:while creating a dynamic web project select Dynamic Web Module Version as 2.5 OR Higher,Make Sure You Check Generate web.xml Deployment Descriptor Box,It will create web.xml file for you otherwise you have to create manually).

So We Have Created Files For Our Project See Below.
Inside Web-Content

login.jsp
loginsuccess.jsp

Inside src Folder

LoginServlet.java class
LogpoutServlet.java class

After Creating All These Files.
Look Inside web.xml
web-content
>Meta-Inf
>Web-Inf
>lib
>web.xml

web.xml should contain.

<welcome-file> tag inside <welcome-file-list></welcome-file-list> tag.
servlet name and servlet class inside <servlet></servlet> tag and now servlet-name and url pattern inside <servlet-mapping></servlet-mapping> tag.

Here we have two jsp files i.e.,
login.jsp and loginsuccess.jsp and
here i want initial page of my application should be login.jsp.
hence my welcome file will be login.jsp.
See Below
<welcome-file-list>
<welcome-file>login.jsp</welcome-file>
</welcome-file-list>

Two servlet i.e.,
LoginServlet.java
url pattern for LoginServlet.java class is getLogin(you will be able to create url pattern while creating a servlet,you can give any name to url pattern).

LogoutServlet.java
url pattern for LogoutServlet.java class is getLogout.

See Below Example Of Our Project's web.xml File.
--------------------------------------------------------
web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">

<welcome-file-list>
<welcome-file>Jsp/html</welcome-file>
</welcome-file-list>

<servlet>
<servlet-name>LoginServlet</servlet-name>
<servlet-class>com.login.LoginServlet</servlet-class>
</servlet>

<servlet-mapping>
<servlet-name>LoginServlet</servlet-name>
<url-pattern>/getLogin</url-pattern>
</servlet-mapping>

<servlet>
<servlet-name>logoutservlet</servlet-name>
<servlet-class>com.login.logoutservlet</servlet-class>
</servlet>

<servlet-mapping>
<servlet-name>logoutservlet</servlet-name>
<url-pattern>/getLogout</url-pattern>
</servlet-mapping>

</web-app>
--------------------------------------------------------------
login.jsp

Here in this login.jsp we have created a form with username and password fields to take input from the user and a submit button to submit the form.
Here we used post method.
Action is getLogin i.e.,when user hit submit button getLogin URL is responsible to process the form parameters and authenticate them.

---------------------------------------------------
<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
pageEncoding="ISO-8859-1"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Insert title here</title>
</head>
<body><br/><br/><br/><br/>

<center>
<h3>Login Form</h3>
<form method="post" action="getLogin">
Username:<input type="text" name="username" /><br/><br/>
Password:<input type="text" name="password" /><br/><br/>
                
<input type="submit" value="Login" style="width:170px;height:34px;">
</form>
</center>
</body>
</html>
-------------------------------------------------------
LoginServlet.java(url pattern is getLogin :)
Here in LoginServlet.java

We are extracting the form parameters and processing them i.e.,username and password.

Setting the content type as text/html.

Getting the PrintWriter object as out through the factory method getWriter() of HttpServletResponse,writer object will help us to print text on browser.

Using the RequestDispatcher Interface for Servlet Collaboration,this interface can be used to include or forward the content of another resource also ex. loginsuccess.jsp, it has two methods include and forward,we can get the instance of RequestDispatcher through factory method i.e., getRequestDispatcher() of HttpServletRequest.

Using the HttpSession interface for session management,HttpServletRequest factory method getSession() provide the instance of HttpSession,using this instance we can set and get session attributes of the session scope.

Now registering the driver for database connection.

Creating the connection by providing url,username and password using the DriverManager class method i.e., getConnection(url,username,password) takes url,username and password as argument.

Now executing the query for checking username and password,if username and password is correct then displaying appropriate message and forwarding the same request to loginsuccess.jsp. or if username or password is incorrect then displaying appropriate message and including the login.jsp again.

If username and password is correct then setting the username in session scope,so on loginsuccess.jsp we can check if user is logged in or not by getting the session attributes.

Thats All For LoginServlet.java
--------------------------------------
package com.login;

import java.io.*;
import java.sql.*;
import javax.servlet.*;
import javax.servlet.http.*;
@SuppressWarnings("serial")
public class LoginServlet extends HttpServlet {

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

response.setContentType("text/html");
PrintWriter out=response.getWriter();
RequestDispatcher rd;
HttpSession session=request.getSession();
Connection conn=null;
try {
Class.forName("com.mysql.jdbc.Driver");
conn=DriverManager.getConnection("jdbc:mysql://localhost:3306/mysql@123","root","");

String username=request.getParameter("username");
String password=request.getParameter("password");

String query="SELECT password FROM login where username=?";
PreparedStatement pst=conn.prepareStatement(query);
pst.setString(1,username);
ResultSet rs=pst.executeQuery();

if(rs.next()){
if( rs.getString(1).equalsIgnoreCase(password)){
session.setAttribute("username", username);
rd=request.getRequestDispatcher("/loginsuccess.jsp");
rd.foward(request, response);
}
else {
out.print("Invalid Password");
rd=request.getRequestDispatcher("/login.jsp");
rd.include(request, response);
}
}

else {
out.print("Invalid Username");
rd=request.getRequestDispatcher("/login.jsp");
rd.include(request, response);
}
}
catch (SQLException e){
out.print(e.getMessage());
}
catch (ClassNotFoundException e) {
out.print(e.getMessage());
}
}//end of main
}//end of class
==============================

loginsuccess.jsp

Here on this page first we are checking by getting the session attribute username that we have set in LoginServelt.java as username using if{} else{} statement.

If we got session.getAttribute("username")==null then
user can't access this page and they will be redirected to login.jsp.

Else user can access this page.

After login we are displaying

<%@ page language="java"
contentType="text/html; charset=ISO-8859-1" pageEncoding="ISO-8859-1"%> <!DOCTYPE html
PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type"
content="text/html; charset=ISO-8859-1"> <title>Insert title here</title> </head> <body><br/> <% if(session.getAttribute("username")==null) { response.sendRedirect("login.jsp"); } else{ String name=session.getAttribute("username").toString(); %> <center>Logged In<br/> <h3>Welcome</h3> <h3> <%=name %></h3> <form method="post" action="getLogout"> <input type="submit" value="Logout?"> </form> </center> <%}%> </body> </html>
when user hit logout button then logoutservlet.java servlet is
responsible to invalidate the sessions.See below example.

logoutservlet.java

In logoutservlet.java we are invalidating the session.

When user hit the logout button on loginsuccess.jsp page this servlet is responsible to invalidate or destroy the sessions,and redirect to initial page of our project application i.e.,login.jsp :).

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.*;

public class logoutservlet extends HttpServlet {

protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {

HttpSession session=request.getSession();
session.invalidate();
response.sendRedirect("login.jsp");
}
}

Hope It Was Helpful :)
Thank You

Team
The Tech Matin

www.thetechmatin.com

Java Insert values in mysql table

2018-10-08T11:55:00.004+05:30

HOW TO INSERT VALUES IN MYSQL DATABASE TABLE USING A JAVA APPLICATION?
Inserting values in mysql database table from a JAVA APPLICATION.

#Steps to insert values in mysql database table.
Create a database and a table with some columns according to your requirement.

#CREATE A DATABASE
TO CREATE A DATABASE EXECUTE THE FOLLOWING STATEMENT.

create database your_database_name; //ex name mysql@123
#NOTE:CREATE DATABASE is a sql command for creating a database.


#NOW CREATE A TABLE IN THAT DATABASE.
  CREATE TABLE IF NOT EXIST your_table_name(
Fname varchar(20) NOT NULL,
Lname varchar(20) NOT NULL
);//ex table name tech-matin

   Thats all for databse and table creation.

NOW CREATING A JAVA APPLICATION IN ECLIPSE.
To create a project in ECLIPSE go to file then click on new and select JAVA PROJECT,give a name to your project and finish creating your project.

Now before proceeding further make sure you have downloaded MYSQL CONNECTOR JAR FILE.

Now add that mysql connector jar file which you have downloaded to your project.

NOW CREATING A CLASS
To create a class right click on src folder in your project and select class,provide package name and class name and finish creating a class(for example class name is MyClass).

import java.sql.*;
import java.io.*;
public class MyClass {
public static void main(String[] args){
try{
String driver,dusername,dpassword,url;
driver="com.mysql.jdbc.Driver";
dusername="root";//default for localhost
dpassword="";//blank for localhost
url="jdbc:mysql://localhost:3306/mysql@123";//url

Class.forName(driver);//Registering the driver
Connection conn=DriverManager.getConnection(url, dusername, dpassword);
System.out.println("Connected");//checking if connected

InputStreamReader myreader=new InputStreamReader(System.in);
BufferedReader read=new BufferedReader(myreader);
System.out.println("Enter Fname");
String Fname=read.readLine();
System.out.println("Enter Lname");
String Lname=read.readLine();

String query="INSERT INTO tech-matin values(?,?)";
PreparedStatement st=conn.prepareStatement(query);
st.setString(1, Fname);
st.setString(2, Lname);
st.executeUpdate();
System.out.println("Inserted");//checking if data inserted successfully
}//end of try
catch(Exception e){
System.out.println("Exception Occured "+e.getMessage());
}//end of catch
}//end of main
}//end of class

#Explanation:
Here In MyClass Class in main method we are performing insertion operation.

First we are creating connection with MySql Database.

To create a connection with MySql database we need to register the driver,url,username and password(See above example).

Now in the next step we are taking input from the user i.e., Fname and Lname using BufferedReader Class that extends Reader Class which take the object of InputStreamReader Class as argument.(See Above Example).

Now in the next step we are executing a String query to insert values in our database table using PreparedStatement.

At last executing the query using executeUpdate() method of PreparedStatement and printing Message if everything goes right.

NOW RUN THE PROGRAM ENTER Fname and Lname and press enter.

#NOW CHECK YOUR DATABASE TABLE IF VALUES INSERTED.

#QUICK REVISION:
#STEPS

-Create Project Add MySql Jar File.
-Create Class And Main Method.

-Register The Driver.
-Create The Connection.
-Create The Statement.
-Execute The Query.

Hope It Will Help You :)

JSP Login System With Mysql Database

2018-10-06T13:09:00.000+05:30

Creating A JSP Login System With MYSQL Databse.

In this article we are going to learn that how to create a simple JSP Login System With MYSQL Database.

Here in this Example we are checking for username and password.

To create a login system using JSP and MySQL Database perform the following steps.

#Open your Eclipse IDE

Create Dynamic Web Project
Add MySql Connector Jar File.
Now in the Web Content Directory Create a JSP Class File with any Name here is ConnectionClassFile.jsp.
Perform the necessary coding to connect to the MySql Database.
Job of this class file is to return the connection Object so its sub classes can use it and perform the database operation by including ConnectionClassFile.jsp.

ConnectionClassFile.jsp

<%@page import="java.sql.*" %>

<%!

public class MyClass{

Connection conn=null;

public Connection MyConnection(){

try{

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

this.conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/mysql@123","root","");

}

catch(Exception ex){

out.println("exception occuered " + ex.getMessage());

}

return conn;

}

NOW CREATE index.jsp file.

index.jsp File In Same Directory.
This index.jsp page is created for User Interface.
when we run our project index.jsp will be displayed in browser if everything goes right.
In this page we have created a text field and a password field to take input from the users and a submit button.
when user hit the submit button after filling the username and password an action(here ActionJsp.jsp is responsible to perform database operation) will be performed,the job of this action JSP is to execute the query to check that the information entered by user is Correct OR Not.
If information is incorrect then display appropriate message and if it correct then perform necessary action.

index.jsp

<body>

Username :<input type="text" name="username"/><br/><br/>

Password :<input type="password" name="password"/><br/><br/>

</form>

</center>

</body>

Now Create ActionJsp.jsp File In Same Directory And Write The Necessary Code To Check Username And Password Is Correct OR Not.

Job Of ActionJsp.jsp

Include the ConnectionClassFile.jsp to access its properties.
Declare PreparedStatement ,Connection ,ResultSet,create the Object of MyClass and declare a String query variable inside declarative tag for further uses.
Extract the form parameters and store into variables inside JSP scriplet tag.
Write the necessary query to check the username and password entered by user is correct or incorrect,See the example.

ActionJsp.jsp

<%@ page language="java" contentType="text/html; charset=ISO-8859-1" pageEncoding="ISO-8859-1"%>

<%@ page import="java.sql.*" %>

<%@ include file="ConnectionClassFile.jsp" %>

<body>

<%!

PreparedStatement ps;

Connection cn;

ResultSet rs;

MyClass obj=new MyClass();

String query;

try{

String username=request.getParameter("username");

String password=request.getParameter("password");

query="select password from login where username=? ";

cn= obj.MyConnection();

ps=cn.prepareStatement(query);

ps.setString(1, username);

rs=ps.executeQuery();

if(rs.next()){

if(rs.getString(1).equalsIgnoreCase(password)){

out.print("Welcome "+username) ;

}

else{

out.print("Invalid Passwpord");

}

else{

out.print("Invalid Username");

}

catch(Exception ex){

out.print ("Sorry an exception occuered " + ex.getMessage());

}

</body>

So in the above example we are taking input from the user and extracting form parameter in ActionJsp.jsp page and checking the username and password entered by user is correct or incorrect by sql query.

If user entered correct username and password then page will display welcome message in the our case.

That’s All

Hope It Will Help You Good Luck ;-)

Creating A JAVA Login System With MYSQL Database Table

2018-10-04T22:42:00.001+05:30

HOW TO CREATE A JAVA LOGIN SYSTEM WITH MYSQL DATABASE?
Hello Guys
In this article i am going to show you...
How to create a java login system with mysql database?
So Lets Begin :)

For that first of all you need to download the platform independent mysql connector jar file.
After downloading jar file,create a project in Eclipse or in your favorite IDE with main method.
Now right click on project,1)now click on configure build path,2)click on Add External Jars,3)Now
find your downloaded mysql connector jar file and click on that and say apply and close.
Now the Referenced Libraries Directory will be created in that jar files are present that you added in last step.
Now in your class in main method or create your own local mehtod perform the following steps.

1)Register the driver
Class.forName("com.mysql.jdbc.Driver");

2)Create the Connection
String url,username,password;
url="mysql:jdbc:jdbc:mysql://localhost:3306/thetechmatin";
//note:thetechmatin is database name.
username="root or your username";//if it is a localhost
password="your password";//if it localhost then keep it blank.

Connection conn=
DriverManager.getConnection(url,username,password);

Thats all for creating connection to database.
Now you can perform execution of queries according to your requirement.

Our Purpose Is To Create A Login System.
#Steps to achieve our target...

Create a mysql database and a table with username and password column.
Insert Some Users Credentials like e.g., username as virat and password as kohli.

Creating a Database:
-use the following statement
create database database_name;
Here i want my database name as thetechmatin;

so execute the following statement
create database thetechmatin;
Thats all for Database Creation.

Now create a Table give name as login,execute the below statement.
create table login
(username varchar(20),
password varchar(20)
);

#So now we have a database thetechmatin and a Table login with column username and password.

#Now Insert values in table
INSERT INTO login(username,password) VALUES('virat','password');

Now Follw These Steps :)
File Name : MyClass.java
import java.sql.*;
import java.io.BufferedReader;
public class MyClass{

public static void main(String[] args) throws
ClassNotFoundException, SQLException, IOException{
String url,username,password;
url="mysql:jdbc:jdbc:mysql://localhost:3306/thetechmatin";
//note:thetechmatin is database name.

username="root";//if it is a localhost
password="";//if it localhost then keep it blank.
Connection conn=
DriverManager.getConnection(url,username,password);
System.out.println("Connected");
//checking the connection if connected

//reading input from the user
BufferedReader read=new BufferedReader(new InputStreamReader(System.in));
System.out.println("Enter Username");
String username=read.readLine();
System.out.println("Enter Password");
String password=read.readLine();

String query="select password from login where username=? ";
PreparedStatement pst=conn.prepareStatement(query);
pst.setString(1,username());
ResultSet rs=pst.executeQuery();

if(rs.next()){
if( rs.getString(1).equalsIgnoreCase(password)){
System.out.println("Logged In");
  //put your code according to your requirement
}
else{
System.out.println("Invalid Password");
}
}
else{
System.out.println("Invalid Username");
}
}//end of main method
}//end of class

In the above example first we registered the Driver class and then we created connection using getConnection() method of DriverManager class by passing URL, Username and Password as argument.
After that we are using Buffered Reader to take input from the user i.e., username and password and then validating them using MySql query and displaying appropriate message.
If user enter valid username and password then Logged In message will be displayed otherwise invalid username or password.

Hope It Will Help You.
Good Luck :)

Connecting a java application with mysql database.

2018-09-02T11:47:00.000+05:30

Connecting a java application with mysql database.

Hello Guys
In this arcticle i have shown how to connect a java application with MYSQL Database Table and fetch data from that table?

First of all you need to download the platform independent mysql connector jar file.
After downloading jar file,create a project in Eclipse or in your favorite IDE with main method.

-Now right click on project
1)now click on configure build path,
2)click on Add External Jars,
3)Now find your downloaded mysql connector jar file and click on that and say apply and close.

-Now the Referenced Libraries Directory will be created, in that jar files are present that you added in last step.

-Now in your class main method or create your own local method perform the following steps.
1)Register the driver
Class.forName("com.mysql.jdbc.Driver");

2)Create the Connection
String url,username,password;
url="jdbc:mysql://localhost:3306/mysql@123";
//note:mysql@123 is a database name.

username="root";//if it is a localhost
password="";//if it localhost then keep it blank.

Connection conn=DriverManager.getConnection(url,username,password);

-That's all for creating connection
-Now you can perform execution of queries according to your requirement.
-Performing SQL SELECT Database Operation In Java Application.
public class MyClass{
public static void main(String args[]){try {
String query="select DISTINCT(ClientName) from clientdetail";
PreparedStatement st=conn.prepareStatement(query);
ResultSet rs = st.executeQuery();

while(rs.next()){
String cname=rs.getString("ClientName");
//it depend on your requireme
System.out.println(cname);
}
rs.close();
st.close();
conn.close();
}
catch(Exception e){
System.out.println(e.getMessage());
}
}
}#Full Example
Class Name MyClass.java
import java.sql.*;
public class MyClass
{
public static void main(String args[])throws ClassNotFoundException
{
Class.forName("com.mysql.jdbc.Driver");
//Registering the deriver
try {
String url,username,password;
url="jdbc:mysql://localhost:3306/mysql@123";
//note:mysql@123 is a database name.

username="root";//if it is a localhost
password="";//if it localhost then keep it blank.
Connection conn=DriverManager.getConnection(url,username,password);

String query="select DISTINCT(ClientName) from clientdetail";
PreparedStatement st=conn.prepareStatement(query);
ResultSet rs =st.executeQuery();

while(rs.next())
{
String cname=rs.getString("ClientName");
//it depend on your requireme
System.out.println(cname);
}
rs.close();
st.close();
conn.close();
}
catch(Exception e)
{
System.out.println(e.getMessage());
}
}
}

#Here database name is mysql@123 and clientdetail is my Table name with ClientName Column, and using SELECT DISTINCT Statement to get Unique ClientName from the table.

Hope It Will Help You.
Thanks