LET's START CORE JAVA !

Simple example of SERVLET !

2014-07-16T23:43:00.000+05:30

Below is the sample program of SERVLET which is taken from known J2EE book ! You can start this example by simply craeting new project in Netbeans and again do right click and select Servlet option and when you do next, make sure you tick on create XML file.

Don't worry if you feeling tense after see this coding but I just want to inform the new guys who are new to the J2EE, the syntax of the coding is fixed and it's already ready for you by netbeans, you just have to do your part of coding in the middle of this.

In this example, this is just the simple small random number program that we see in core java but the difference is, this is ruining on web browser. Here, I have write the name of the servlet is GuessWhat but you can name it whatever you like so don't worry about that.

import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class GuessWhat extends HttpServlet {


protected void processRequest(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html;charset=UTF-8");
try (PrintWriter out = response.getWriter()) {

String d1=Integer.toString((int)((Math.random()*99)));
String d2=Integer.toString((int)((Math.random()*99)));


out.println("<html> <body> "+ "<h1 align=centre>Let's guess the number by pressing F5</h1>"+
"<h2> This time " + d1 + " and "+ d2 +" are the right answer, now time to guess another numbers !</h2>"+"</body>"+"</html>");

}
}

@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
processRequest(request, response);
}

@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
processRequest(request, response);
}


@Override
public String getServletInfo() {
return "Short description";
}

}

Simple program of "Thread" !!!!!

2013-12-18T23:50:00.000+05:30

In this program, we are creating two thread and give them different sleep time. With the help of "Thread.sleep()" you can write down the milliseconds so that thread can start run after defined seconds. And to start the thread, we simple write "t1.start()" in this program, to start the particular thread. And in the last, "t1.isAlive()" is the boolean method to check the thread, whether it is alive or not !

In below program, we give 5 to 1 to first thread and 6 to 1 to second. When both threads are start than it stops for the milliseconds that we wrote different for both of them so that you can identify that which thread is complete running and complete first. And for that, we also wrote the message that "Exit from xyz thread now........." for confirmation from thread !

class createThread extends Thread{

public void run(){
try{
for(int i=5;i>0;i--){
System.out.println(i);
Thread.sleep(500);
}
}catch(InterruptedException e){}
System.out.println("Exit from first thread now.....");
}
}

class createThread2 extends Thread{

public void run(){
try{
for(int j=6;j>0;j--){
System.out.println(j);
Thread.sleep(1000);
} }
catch(InterruptedException e){}
System.out.println("Exit from second thread............");
}

}

public class trythread {

public static void main(String[] args) {

createThread t1= new createThread();
createThread2 t2=new createThread2();
t1.start();
t2.start();
System.out.println("First thread is alive: "+t1.isAlive());
System.out.println("Second thread is alive: "+t2.isAlive());
}

}

____________________________________________________

Output:

First thread is alive: true

Second thread is alive: true

Exit from first thread now.....

Exit from second thread............

Using "super" keyword in example of inheritance

2013-11-12T23:11:00.001+05:30

In below program we use method overriding, in method overriding if we haven;t use "super" keyword than you can not use it. In below program, we use "super" keyword in getdata and displaydata which we already used in first class and now when we inherit the second class than we are using method overriding that mean we using same method in second class, now to access the parent class member you can use "super" key word and we did same thing here. You can also use "super" keyword to call parent class constructor within child class constructor.

import java.io.*;

class empl{

int empno;
String name;
String position;
int ph;

void getdata()throws IOException
{

DataInputStream e = new DataInputStream(System.in);

System.out.println("Enter employee number: ");
empno = Integer.parseInt(e.readLine());

System.out.println("Enter your name: ");
name = e.readLine();

System.out.println("Enter the employee position: ");
position=e.readLine();

System.out.println("Enter the phone number: ");
ph = Integer.parseInt(e.readLine());

}

void displaydata() {

System.out.println(empno+"\t"+name+"\t"+position+"\t"+ph);

}

}

class manager extends empl{

int salary;
String secname;

void getdata() throws IOException{

super.getdata();

DataInputStream e= new DataInputStream(System.in);

System.out.println("Enter salary: ");
salary=Integer.parseInt(e.readLine());

System.out.println("Enter second name: ");
secname= e.readLine();

}

void displaydata(){
super.displaydata();
System.out.println(salary+"\t"+secname);
}
}
class inheritt{
public static void main(String []args) throws IOException{

manager e1= new manager();
manager e2= new manager();

e1.getdata();
e2.getdata();

e1.displaydata();
e2.displaydata();

}
}
____________________________________
Output:

Enter employee number:

Use of "this" keyword with very simple example

2013-11-10T15:42:00.000+05:30

class thiss{

int a,b;

thiss(){

a=1;
b=2;}

thiss(int c,int d){
this();
this.a=c;
this.b=d;

}

void displaydata(){

System.out.println("c= "+a);
System.out.println("d= "+b);
}

public static void main(String []arg){

thiss t1= new thiss();
t1.displaydata();

thiss t2= new thiss(3,4);
t2.displaydata();
}}

___________________
Output:

c= 1;
d=2;
c= 3;
d=4;

Example program of geting data from user using Wrapper Class

2013-10-26T23:31:00.000+05:30

In below program, we will convert instance variable into wrapper class!

If you want to get data from user, you must have to import the java class from library, you can do this by import weather "java.io", "java.util" or "java.scanner", you can use any one of this !

import java.io.*;

public class employee{

int empnumber;
String name;
String add;

private void getdata()throws IOException{

DataInputStream d = new DataInputStream(System.in);

System.out.println("Enter Employee Number: ");
empnumber= Integer.parseInt(d.readLine());

//here we convert integer into wrapper class

System.out.println("Enter Emplyee Name: ");
name = d.readLine();

//in both string value,we haven't convert because String is a class not variable so no need to convert in to wrapper class

System.out.println("Enter Employee Address: ");
add=d.readLine();
}

private void display()throws IOException {

System.out.println(empnumber+"\t"+name+"\t"+add);

}

public static void main(String args[])throws IOException{

employee e1 = new employee();
employee e2 = new employee();

e1.getdata();
e2.getdata();

e1.display();
e2.display();
}
}

Facts about Constructor with an example...............

2013-10-26T18:35:00.001+05:30

Some facts that you should know about Constructor.....................

It has the same name as the classname.
It is used to initialize the object that means it is used to construct the object.
It does not have any return type.
It can have arguments.
The constructor without argument is called default constructor.
A class can have more than one constructor but they must be different from each other by

- Number of arguments or
- Type of arguments or
- Sequence of arguments
This concept is called constructor overloading.

It is automatically called when an object is created.

Simple example to explain constructor in program.

___________________________________________

import java.io.*;

class cons

{

int a,b;

cons()//defulat constructer

{

a=10;

b=20;

System.out.println("default constructer");

}

cons(int p,int q)//parametrised constructer

{

a=p;

b=q;

System.out.println("parametrised constructer");

}

cons(int p)//one parametrised constructer

{

a=p;

b=25;

System.out.println("one parametrised constructer");

}

void show()

{

System.out.println("a = "+a);

System.out.println("b = "+b);

}

public static void main(String arg[])throws IOException

{

cons c1=new cons();

c1.show();

cons c2=new cons(10);

c2.show();

cons c3=new cons(100,200);

c3.show();

cons c4=new cons();

c4.show();

cons c5=new cons();

c5.show();

cons c6=new cons(1000,2000);

c6.show();

cons c7=new cons(5000,10000);

c7.show();

}

Searching value and Reverse code !!!!!!

2013-01-01T01:09:00.000+05:30

public class FindandReverse {

/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub

int i[] = {1,2,3,5,6};

int searchVal = 55;

boolean found = false;

for(int a = 0; a<i.length;a++){

if(i[a]==searchVal){

found = true;}
}

if(found){

System.out.println("We found the value "+ searchVal+ "! " );

}
else{

System.out.println("Can't find "+searchVal+ " in this array.");

}

// ********************************************************

int x= 123456;

int temp = 0;

int reverse = 0;

while(x>0){

temp = x%10; //get the value from right of x

reverse = reverse * 10 + temp; //add the value to the reverse
x = x/10; //remove the value from the x

} System.out.println("\n"+reverse);

}
}

_________________________________________________

Output:

Can't find 55 in this array.

654321

Multithreading in Java !!!!!

2012-12-12T17:51:00.000+05:30

A multiprocessor system can actually do more than one thing at at time but with Java threads, it can appear that you are doing several things simultaneously. Execution can move back and forth between stacks so rapidly that you feel as though all stacks are executing at the same time.

Thread t = new Thread(r);

Thread is a class in the java.lang package. And this package is imported by default even without package declaration. A Thread object represents a thread of execution, you will create an instance of class Thread each time you want to start up a new thread of execution.

Three states of new thread

When thread is new !

A thread instance has been created but not started. In other words, there is a Thread object but no threa of execution.

When thread is in Runnable state ! (t.start();)

When you start the thread, it moves into the runnable state. This means the thread is ready to run and just waiting for its chance to be selected for execution.

When thread is in Running state !

Only the JVM thread scheduler can make that decision. You can sometimes influence that decision but you can not force a thread to move from runnable to running.

The thread scheduler can move a running thread into blocked state for a variety of reasons. The scheduler will move the thread out of the running state until something becomes available. It can put the thread in sleep by sleep(). You can force the currently running thread to leave the running state and give chance to another thread to run. In the sleep() method, that's for sure that sleeping thread will not become the currently running thread before the length of sleeping time has expired.

And how will you apply the sleep() method, that also simple, just write down Thread.sleep(1000); This mean the current thread will not be execute till 1 second. Everything we write down in this method is in milliseconds.

When you pass a Runnable to a Thread constructor, you are really just giving the Thread a way to get to a run() method. You are giving the Thread its job to do.

___________________________________________

Here I am giving the example of Thread which is taken from Head First Java book for your reference :

In this example we took two thread and give there name and also set small scenario like what happen if one of the thread sleep or wake up that is runnable and what happen if there is not enough money for them in bank account.

class BankAccount{

private int balance = 100;

public int getBAalance(){
return balance;
}
public void Withdraw (int amount){
balance = balance - amount;
}
}

public class RyanAndMonicaJob implements Runnable {

private BankAccount account = new BankAccount();

public static void main(String[] args) {

RyanAndMonicaJob theJob = new RyanAndMonicaJob();
Thread one = new Thread(theJob);
Thread two = new Thread(theJob);

one.setName("Ryan");
two.setName("Monica");
one.start();
two.start();

}

public void run(){
for(int x = 0; x<10;x++){
makeWithdrawl(10);
if(account.getBAalance() < 0){
System.out.println("Overdrawn!");
}
}
}

private void makeWithdrawl(int amount){

if(account.getBAalance() >=amount){
System.out.println(Thread.currentThread().getName()+" is about to withdrawl.");
try{
System.out.println(Thread.currentThread().getName()+ " is going to sleep.");
Thread.sleep(500);
}catch (InterruptedException ex){ex.printStackTrace();}
System.out.println(Thread.currentThread().getName()+" woke up.");
account.Withdraw(amount);
System.out.println(Thread.currentThread().getName()+" completes the withdrawl.");
}
else{
System.out.println("Sorry,not enough for " + Thread.currentThread().getName());
}
}
}

_____________________________________________

Output:

Ryan is about to withdrawl.
Monica is about to withdrawl.
Ryan is going to sleep.
Monica is going to sleep.
Ryan woke up.
Monica woke up.
Ryan completes the withdrawl.
Monica completes the withdrawl.
Ryan is about to withdrawl.
Monica is about to withdrawl.
Ryan is going to sleep.
Monica is going to sleep.
Ryan woke up.
Ryan completes the withdrawl.
Ryan is about to withdrawl.
Ryan is going to sleep.
Monica woke up.
Monica completes the withdrawl.
Monica is about to withdrawl.
Monica is going to sleep.
Ryan woke up.
Ryan completes the withdrawl.
Ryan is about to withdrawl.
Ryan is going to sleep.
Monica woke up.
Monica completes the withdrawl.
Monica is about to withdrawl.
Monica is going to sleep.
Ryan woke up.
Ryan completes the withdrawl.
Ryan is about to withdrawl.
Ryan is going to sleep.
Monica woke up.
Monica completes the withdrawl.
Monica is about to withdrawl.
Monica is going to sleep.
Ryan woke up.
Ryan completes the withdrawl.
Ryan is about to withdrawl.
Ryan is going to sleep.
Monica woke up.
Monica completes the withdrawl.
Sorry,not enough for Monica
Sorry,not enough for Monica
Sorry,not enough for Monica
Sorry,not enough for Monica
Sorry,not enough for Monica
Ryan woke up.
Ryan completes the withdrawl.
Overdrawn!
Sorry,not enough for Ryan
Overdrawn!
Sorry,not enough for Ryan
Overdrawn!
Sorry,not enough for Ryan
Overdrawn!
Sorry,not enough for Ryan
Overdrawn!

_____________________________________________

Understand Wrapper and parse !!!

2012-12-10T15:43:00.000+05:30

Practically Wrapper mean wrap the primitive in different value, so that we can use it as per the situation.

There is wrapper class for every primitive in java. The wrapper class for int is Int, float is Float, char is Character, byte is Byte, double is Double and so on.

Integer int1 = new Integer("4");
Integer int2 = new Integer("1");
Double int3 = new Double(123.12);

i = int2 + int1;
System.out.println(i); //5

When we convert the value of wrapped numeric to a primitive than we use following value() methods. That mean we put byteValue(), doubleValue() and so on.

byte b = int1.byteValue();
System.out.println(b);

short s = int3.shortValue();
System.out.println(s);

double d = int2.doubleValue();
System.out.println(d);

Following example show the created value of int4 is 5, cause when you convert binary of 101 than you will get 5. So int = 5 now. This is called valueOf() method.

Integer int4 = Integer.valueOf("101",2);
System.out.println(int4);

Now we look on some parseXxx() method, it is nearly like valueOf() method.
Following example is for converting string to other primitive what ever you like to apply.

double d1 = Double.parseDouble("789.456");
System.out.println(d1);

long l1 = Long.parseLong("101",2);
System.out.println(l1);

Now above example is same like we apply in valueOf() methos, we get same output but using different method.



Now when we use toXxxString() method than it convert the following:

String s1 = Integer.toHexString(123);
System.out.println(s1); // 7b

String s2 = Long.toOctalString(123);
System.out.println(s2); //173

String s3 = Double.toHexString(789);
System.out.println(s3); //0x1.8a8p9

Now toString(), in this method you can convert every primitive values to string:

Long l = new Long("789456123");
System.out.println(l.toString()); //789456123

String l2 = Long.toString(789456123);

You can take different primitive value.

Understand Abstract class and Interface !!!

2012-12-04T00:47:00.000+05:30

Abstract class and Methods

- An Abstract class can not be instantiated but they can be subclassed.

- An Abstract method is method that is declared without an implementation without braces and followed by semicolon.

Example:

public abstract class Animal{

abstract void eat();

}

- All abstract methods must be implemented in the first concrete subclass in the inheritance tree.

- An abstract class can have both abstract and non abstract methods.

- When you don't want a class to be instantiated mark the class with abstract keyword.

- If a class has even one abstract method, the class must be marked abstract.

We have here AnimalObject in above image, might be all three sublcass that is Lion, cat and zebra behave totally different but other thing we find common is eat and roam. You can take advantage of similarities and declare all the animals to inherit from the same abstract object. Lion , Cat and Zebra inherit from Animal.

Example:

public abstract class Animal{

abstract void eat();

abstract void roam();

}

class Lion extends Animal{

void eat();{

}

void roam();{

}

class Cat extends Animal{

void eat();{

}

void roam();{

}

class Zebra extends Animal{

void eat();{

}

void roam();{

}

Now all this above three non abstract subclass of Animal that is Lion, Cat and Zebra must provide implementation.

Interface

- An interface is a reference type similar to a class that can certain only constants method signature and nested types. There are no method bodies.

- Use interface when you want different behavior different classes.

- Interface can not be implemented by class or extended by other interfaces.

- Create an interface using the "interface" keyword instead of class.

Example:

public interface mainInterface extend Interface1, Interface2, Interface3{

void doSomething (int a, float y);

int doSomethingElse(String s);

}

The public access specifier indicates that the interface that the interface can be used by any class in any package. If you do not specify that the interface is public, your interface will be accessible only to classes defined in the same package as the interface.

An interface can extend other interfaces just as a class can extend or subclass another class. As you know that the class can only extend other class but interface can extend any number of interfaces. And it declare by comma as shown in above example.

Thank you for your time..............

It is important to know this example that is, How to merge both array in single variable !!!!

2012-11-27T00:19:00.000+05:30

Below program provide you the reference regarding merging both array in other !

_______________________________________

public class Array {

public static void main(String[] args) {
// TODO Auto-generated method stub

int A [] = {1,2,3,4,5};

int B [] = {6,7,8,9,10};

int C[][] = {A,B};

int la = A.length;
int lb = B.length;

System.out.print("ARRAYS in A: ");

for(int x = 0; x<la;x++){
System.out.print(" "+A[x]);
}

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

System.out.print
("ARRAYS in B: ");

for(int y=0;y<lb;y++){
System.out.print(" "+B[y]);
}

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

System.out.print("Arrays in C: ");

for(int i = 0; i<C.length;i++){

for(int j= 0;j<C[i].length;j++){
System.out.print(C[i][j]);
}
}
}
}

_______________________________________

Output:

ARRAYS in A: 1 2 3 4 5

ARRAYS in B: 6 7 8 9 10

Arrays in C: 12345678910

________________________________________

In above programme, we use two dimensional array C[] [] to merge the A[] and B[] single array !!!

Hope you enjoy this simple but important programme !

Apply STACK class in code !!! (java.util.Stack)

2012-11-24T20:16:00.001+05:30

Why we use STACK class?

Normally STACK class is not in use that much except in some programme where there is necessary to apply that. In STACK class it use LIFO method that is Last in First Out. For example if you push 1 2 3 4, it will pop like 4 3 2 1. You can see same thing happen in our below code. In STACK we use keyword like 'push' and 'pop', most of you guys know this because same thing we use in couple of algorithms. 'pop' mean removed and 'push' mean inserted, that's very easy. To call this class we write 'import java.util.Stack' in starting of the code.

__________________________________________________

import java.util.Stack;

public class Stack1 {

/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub

Stack number = new Stack();

for(int x = 10;x>=1;x--){

number.push(new Integer(x));
}

while (!number.empty()){
System.out.print(number.pop());
System.out.print('-');
}
System.out.println("That's enough now !");
}

}

____________________________________________________

Output:

1-2-3-4-5-6-7-8-9-10-That's enough now !

_________________________________________________

In above programme, we start from 10 and till 1 so when it will pop than it is start from correct sequence that is 1 2 3 4 and so on..........

Hope you guys like this.................

If you find this post useful than please share it to your friends..............

An example including all STRING METHODS !!!

2012-11-20T00:23:00.003+05:30

Meaning of String methods used in this example:

toUpperCase = To make all word capital
toLowerCase = To make all word small
concat = To concatenates both word
trim = To trim the unnecessary space from sentence
replace = To replace old character to new character
indexOf = Showing position of given character
compareTo = compare with another string
compareToIgnoreCase = compare but also ignore on given condition
equals = compare both string, if it is equal than its true
equalsIgnoreCase = compare both string and also ignore case of some characters
______________________________________________

public class Stringexample {

static String firstname = new String ("HARDIK");

static String lastname = new String ("VYAS");

public static void main(String[] args) {
// TODO Auto-generated method stub

int f = firstname.length();
int l = lastname.length();

System.out.println("Showing the length of words: "+f+" "+l);
System.out.println("Calling both from string: "+firstname+ " " + lastname);
System.out.println(" ");

String lcase = firstname.toLowerCase();
String lcase1 = lastname.toLowerCase();

System.out.println("Change it to lower case of spelling: "+lcase+" "+lcase1);

String ucase = lcase.toUpperCase();
String ucase1 = lcase1.toUpperCase();

System.out.println("Change it to upper case of spelling: "+ucase+" "+ucase1);

System.out.println(" ");

String c= firstname.concat(lastname);
System.out.println("Use of concat method: "+c);

String senten = (" GAME IS OVER ! ");

String sentence =senten.trim();

System.out.println("Trim the unnecessary space from sentence: "+ sentence);
System.out.println(" ");
System.out.println("Using replace method: "+senten.replace(' ', '*'));

System.out.println(" ");
String allname = "john! smith. larry, harry/";

int position = allname.indexOf(',');

System.out.println("Position of any symbol or character that you define in index of method: "+position);

String name = "john";
String name2 = "johneeeee";

int compare = name.compareTo(name2);

System.out.println("Comapre method: " +compare);

System.out.println(" ");

int compar = name2.compareToIgnoreCase(name); // using below if else condition to give output of this kind of boolean method

if(compar==0){
System.out.println("Both r eqaull");
}else if(compar>0){
System.out.println("name2 is greater than name");
}else{
System.out.println("name is greater than name2");
}

System.out.println(" ");

System.out.println(name2.equals(name)); // this is one of boolean method

System.out.println(name.equalsIgnoreCase(name)); // this boolean method is for ignore same word

}
}
___________________________________________

Outout:

Showing the length of words: 6 4
Calling both from string: HARDIK VYAS

Change it to lower case of spelling: hardik vyas
Change it to upper case of spelling: HARDIK VYAS

Use of concat method: HARDIKVYAS
Trim the unnecessary space from sentence: GAME IS OVER !

Using replace method: *GAME**IS**OVER*!*

Position of any symbol or character that you define in index of method: 18
Comapre method: -5

name2 is greater than name

false
true

______________________________________

When you start looking at program than you might be think as confusing that from where to start read it or what ever but when you copy it to your tool than you come to know the real scenario.

When you copy this code and try it your self than and only than you come to know the reason or try to copy the same and do some change it and than write new code so that you can better understand your self confidently.

I hope that above example will help you a lot,

Thank you for your time..............

Addition table with help of TWO DIMENSIONAL ARRAY !!!

2012-11-18T23:42:00.001+05:30

Here is the program of addition table with help of two dimensional array and you can also create multiplication or subtraction table !

____________________________________

public class Table {

public static void main(String[] args) {
// TODO Auto-generated method stub

int row = 17, column = 17;

int product[][]= new int [row] [column];

System.out.println(" ");

for(int i = 1; i<row;i++){
for(int j = 0; j< column; j++){

product[i][j] = i +j;

System.out.print(" "+product[i][j]);
}
System.out.println(" ");
}
}
}

_______________________________________

Output:

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19

4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21

6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22

7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26

11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27

12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28

13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29

14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31

16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32

_______________________________________________________

Example of Inheritance and types of Inheritance !!!!

2012-11-15T00:08:00.000+05:30

In Java there are four types of Inheritance

1) Single Inheritance (one super class)
2) Multilevel Inheritance (several super class)
3) Hierarchical Inheritance (one super class many sub-classes)
4) Multiple Inheritance (derived from derived class)

Single Inheritance Hierarchical Inheritance

Multilevel Inheritance   Multiple Inheritance

________________________________________________

public class Multi {
int multi1;
int multi2;

multi(int a, int b){ // constructor method
multi1 = a;
multi2 = b;
}

int result(){ //definition of method

return(multi1 * multi2);
}
}

class multi1 extends multi{
int multi3;

multi1(int a, int b, int c){   // constructor method

super(a,b); // super keyword only used in constructor method

multi3 = c;

}
int result1(){ //definition of method
return(multi1 * multi2 * multi3);
}
}


class total{ // class with main method

public static void main(String [] args){

multi1 multii = new multi1(1,2,3); //creating object

System.out.println("Total will be: " +multii.result1());


}
}
__________________________________________

Output:

Total will be: 6

________________________________________

Above example is just Single Inheritance example !

Get benefit from "? :" Ternary (shorthand for if-then-else statement) operator !!!!!

2012-11-11T15:12:00.000+05:30

Here I am going to write simple code of if else condition.

_______________________________________________

public class Newoperator {

/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub

int x =1;
int y=2;

if(x<y){
x =1;
}else{
x =0;
}
System.out.println(x);
}

}
______________________________________________

Ooutput:

1
_____________________________________________

Now using new operator that is "?" and ":"
__________________________________________________

public class Newoperator {

/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub

int x =1;
int y=2;

x = (x<y) ? 1 : 0;

System.out.println(x);
}
}

_________________________________________________

Output:
1
_______________________________________________

What do you think, what magic happen with this new code, this is all about using ? and :

You can apply same in your regular code to reduce your compile time and make your software efficient.

Try on your own and see the difference................................

Enjoy Java with SWITCH Statement !!!

2012-11-11T14:03:00.000+05:30

public class DoSwitch {

/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub

int dj =7;

switch(dj)
{
case 1: System.out.println("David Guetta");
break;

case 2: System.out.println("Tiesto");
break;

case 3:
case 4:
case 5: System.out.println("Deadmau5");
break;

case 6: System.out.println("kaskade");
break;

default : System.out.println("U must listen all dj before u select !");

}
}

}

______________________________________________

Output:

U must listen all dj before u select !

_____________________________________________

In this program, we are using "switch statement" to select from different case. Just declare the variable you want in your code and put it beside switch. In switch statement, we have to write case word to make it different from each case and also give them numbers so whenever we enter that number than we can call particular result which is there in particular number. This is small example of big program where we have to select from many option.

In the above code, you can see that "break" word which really help to break the rest of the option. Just try to remove all "break" and you can see if you select number 1 than all other option will be printed in output. If you put break than that case break itself and it will be ignore other options.

Now as you can see that I write "case 3 and 4" empty, this mean what ever I write in "case 5" mean result in "case 3 and 4". Here "case 5" is "Deadmau5" and so if you write number 3 than still it show you same result that is Deadmau5.

You might be surprise that why we write default, because if you write the option that is not exist in this program than it will show that message. In this program, if you write any number than 1 to 7 than it show you default message.

Thank you for your time.................

MULTIPLICATION TABLE !!!

2012-11-09T00:10:00.000+05:30

public class multiplicationtable {

/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub

int x = 2;
int z;

for(int y = 1; y<=10;y++){

z = x * y;

System.out.println(x+" * "+y+ " = "+z);

}
}
}

_____________________________________________

Output:

2 * 1 = 2

2 * 2 = 4

2 * 3 = 6

2 * 4 = 8

2 * 5 = 10

2 * 6 = 12

2 * 7 = 14

2 * 8 = 16

2 * 9 = 18

2 * 10 = 20

___________________________________________________________

Same way you can change the sign to + or - and create new addition or deduction table.

Good to know "Enhanced for loop" !!!

2012-11-08T23:09:00.005+05:30

First I want to show you the program of enhanced for loop,

____________________________________________________

public class ForLoop {

public static void main(String[]args){

int numbers[] = {55,120,199,500,708,854,918,999,1000,1012,5000};

for(int x : numbers){

if(x>50 && x<=1000){

System.out.println("Your numbers list is "+x);
}
}
}
}
_________________________________________________

Output:

Your numbers in array list is 55
Your numbers in array list is 120
Your numbers in array list is 199
Your numbers in array list is 500
Your numbers in array list is 708
Your numbers in array list is 854
Your numbers in array list is 918
Your numbers in array list is 999
Your numbers in array list is 1000

__________________________________________________

Now in above program what we did new is write for loop in new way that is put " : " between it. Why we use enhanced loop. It's easy to use when we deal with arrays. Yes, arrays. If you write a code in simple manner than how could you write is? Like as I write this.................

_________________________________________________

public class ForLoop {

public static void main(String[]args){

int numbers[] = {55,120,199,500,708,854,918,999,1000,1012,5000};

for(int x=0; x<=11;x++){

if (numbers[x]>50 && numbers[x]<=1000){

System.out.println("Your numbers in array list is "+numbers[x]);
}
}
}
}
________________________________________________

Output:

Your numbers in array list is 55
Your numbers in array list is 120
Your numbers in array list is 199
Your numbers in array list is 500
Your numbers in array list is 708
Your numbers in array list is 854
Your numbers in array list is 918
Your numbers in array list is 999
Your numbers in array list is 1000

__________________________________________________

Now you can see the difference in both program and you can find that it's easy to define in enhance for loop rather than simple for loop. It also give you accurate output.

Now you also might be surprise that why we get output till 1000 and the numbers written in arrays are till 5000. That's all because of "&&" , "and" condition mean both condition must be fulfill and only after that it give you the output.

Now just change "&&" to "||", now you can see the out put till "5000" that's because "or" condition, according that any one condition must be fulfill so that we can go ahead.

Thanks for spend your valuable time.....................

Power of 2 with "for" loop and "if else" condition !!!!

2012-11-07T23:56:00.001+05:30

public class PowerOf2 {

/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub

int x;
long y =1;
System.out.println("X This is called power of 2\n");

for(x =1; x <=10; x++){

if(x==1){
y = 1;
}
else{
y = y * 2;
}
System.out.println( x + " "+y);
}
}

}

___________________________________________

Output:

X This is called power of 2

1 1

2 2

3 4

4 8

5 16

6 32

7 64

8 128

9 256

10 512

_____________________________________________________________

Program to know how many ODD or EVEN numbers in list!!!

2012-11-04T19:18:00.003+05:30

You can find the explanation on bottom of this post...............
-----------------------------------------------------------------

public class IfElse {

public static void main(String[]args){

int numb [] = {1,2,3,4,5,6,7,8,9,0,111,222,444,888,999,666}; // our list

for(int x = 0; x <numb.length;x++)

if ((numb[x] %2 )==0){

System.out.println(numb[x]+" is even number in this list.");

}

else{

System.out.println(numb[x]+" is odd number in this list.");

}
}
}

_________________________________________________

Output:

1 is odd number in this list.
2 is even number in this list.
3 is odd number in this list.
4 is even number in this list.
5 is odd number in this list.
6 is even number in this list.
7 is odd number in this list.
8 is even number in this list.
9 is odd number in this list.
0 is even number in this list.
111 is odd number in this list.
222 is even number in this list.
444 is even number in this list.
888 is even number in this list.
999 is odd number in this list.
666 is even number in this list.

________________________________________________

Above program is easy to understand but might be some of you confuse about "if ((numb[x] %2 )==0)", we write this because each time all number should be divided by "2", now you better know that which number could be divided to "2", of course even numbers only and rest of the number will be odd number and why we write "==0" this mean if we divided "2" with even number than remainder will be only "0" left and it prove that it is even number.

Now I hope your doubt is solved now,

Thank you for your time.........................

A Trick which help every new Java programmer and also "FOR" loop program for decrements of numbers, inside this post !!!!!

2012-10-28T18:15:00.002+05:30

Hey guys, this time I want to tell you one short key so that you don't have to write down full line for example write down the "syso" and press Ctrl + Spacebar, now tell me what you got. Of course "System.out.println();" and you can use same keys for other keywords. You don't need to writedown all words, just write starting words and press this keys then you got what you want. Isn't that cool ???? I hope this small trick help you a lot till you become professional Java programmer that is for lifetime.

Now in this post I just present small program of number decrements. And here it is.

________________________________________________

public class SimpleFor {

public static void main(String[]args){

for(int x=1; x<=21; x++){

for(int y = 1; y<=x;y++){

//System.out.print(" ");

System.out.print(x);
}

System.out.println(" ");
}
}

}

________________________________________________________________

OUTPUT:

333

4444

55555

666666

7777777

88888888

999999999

10101010101010101010

1111111111111111111111

121212121212121212121212

13131313131313131313131313

1414141414141414141414141414

151515151515151515151515151515

16161616161616161616161616161616

1717171717171717171717171717171717

181818181818181818181818181818181818

19191919191919191919191919191919191919

2020202020202020202020202020202020202020

212121212121212121212121212121212121212121

Now if you remove that "//" from "syso" from the above code, you know what I mean, then you got following output:

2 2

3 3 3

4 4 4 4

5 5 5 5 5

6 6 6 6 6 6

7 7 7 7 7 7 7

8 8 8 8 8 8 8 8

9 9 9 9 9 9 9 9 9

10 10 10 10 10 10 10 10 10 10

11 11 11 11 11 11 11 11 11 11 11

12 12 12 12 12 12 12 12 12 12 12 12

13 13 13 13 13 13 13 13 13 13 13 13 13

14 14 14 14 14 14 14 14 14 14 14 14 14 14

15 15 15 15 15 15 15 15 15 15 15 15 15 15 15

16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16

17 17 17 17 17 17 17 17 17 17 17 17 17 17 17 17 17

18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18

19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19

20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20

21 21 21 21 21 21 21 21 21 21 21 21 21 21 21 21 21 21 21 21 21

Now you can see the difference that is space matters a lot. Right guys???

What happen if we use "casting" on different variables?

2012-10-28T15:32:00.001+05:30

Hi everyone,

Today, I am giving you some information about casting. so What is casting !!!

Casting is taking the same value of variable into other variable. e.g if we assume that "int i = 456123789;" and "byte b = 100;" than if we want to store the value of byte in integer i than we will write "int i1 = (int)b;" now "int i1 = 100;" too. This is called widening.

And on opposite side if we call int value in bye than we will write "byte b1 = (byte) i;" This is called narrowing.

But narrowing always cause the loss of information. Because you already know the reason, this is same as "We try to keep a book in a pencil box where we can only keep the pencil because pencil box is very small". Same thing is happening here.

Now we see the Java code of above variable and try to see the difference.

____________________________________________________

public class Casting {

/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub

int i = 456123789;
byte b = 100;

System.out.println("Normal value");

System.out.println(" ");

System.out.println("i = "+i);
System.out.println("b = "+b);

System.out.println(" ");

System.out.println("Now after using Narrowing");

byte b1 = (byte) i;

System.out.println("b1 = "+b1);

System.out.println(" ");
System.out.println("After using widening");

int i1 = (int)b;

System.out.println("i1 ="+i1);

}

}

____________________________________________________
OUTPUT:

Normal value

i = 456123789
b = 100

Now after using Narrowing
b1 = -115

After using widening
i1 =100

________________________________________________________________________

We got b1 = -115 which is value of integer and real value of integer is 456123789, now you can see that, it is the loss of data.

If we put integer value in byte than the value going to change but if we use byte in integer than we get same value that is 100.

You can check this for your self by using different variables and enter different values.

Use "Debug" to find errors in Eclipse !

2012-10-26T21:39:00.001+05:30

Hi guys,

You might be don't know that you can check your program in eclipse that is how it work, step by step, each movement.

For that you have to do double click on left side of your code as per below image. That "blue dot" mean the debugging of that code will start from that start point that you mention by double clicking.

Now to start the debug you have to select the "Debug" option from toolbar from "Run" tab. You can also press F11 as short key to start.

After start debugging, you might see below image.

Now on right side corner of this image, you can see step behave as you press F6 step by step and on bottom side there is result of the code and that also show step by step not the full result at one time.

Now after finish your debug, you can terminate it by press red button that is shown in below image on left side or press Ctrl + F2 and back to normal Java mode by press Java on right side of below image.

This really help a lot to understand any code step by step throughout Java.

Hope you like this post..............................

Use "FOR" loop to create "PYRAMID" !!

2012-10-26T20:20:00.002+05:30

This is the second "for" loop program to create design, in this post we are going to create the "Pyramid".

What do you think, Is it complicated or not?

Of course not !!!!!!!

^
^ ^
^ ^ ^
^ ^ ^ ^
^ ^ ^ ^ ^
^ ^ ^ ^ ^ ^
^ ^ ^ ^ ^ ^ ^
^ ^ ^ ^ ^ ^ ^ ^
^ ^ ^ ^ ^ ^ ^ ^ ^
^ ^ ^ ^ ^ ^ ^ ^ ^ ^
^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^
^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^
^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^
^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^
^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^
^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^
^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^
^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^
^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^
^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^

Here is the code........................................

public class Pyramid {

/**

* @param args

public static void main(String[] args) {

// TODO Auto-generated method stub

int height = 20;

for(int x=1;x<=height;x++){

for(int y=1;y<=(height-x);y++){

System.out.print(" ");

}

for(int z=1;z<x;z++){

System.out.print("^ ");

}

System.out.print("^");

System.out.println();

}

You can replace "^" with any other symbol you like. And also try to do debug of this program to understand it step by step.