How to run a Java program in Linux

Java (JDK) installation:
Download the latest jdk from sun's website http://java.sun.com/javase/downloads/index.jsp
e.g.; 
jdk-6u20-linux-i586.bin

now make this bin file executable.

chmod +x jdk-6u20-linux-i586.bin

To execute the bin file, type

./jdk-6u20-linux-i586.bin

Agree the License agreement. It will extract the content of bin file into a directory named jdk1.6.0_20
rename this directory to jdk1.6

mv  jdk1.6.0_20  jdk1.6

Now move this directory to /usr/share/

sudo mv jdk1.6 /usr/share/

set path to the java bin directory

export PATH=$PATH:/usr/share/jdk1.6/bin

or make it permanent in .bashrc file of your user's home directory

vim .bashrc

export PATH=$PATH:/usr/share/jdk1.6/bin

save and close this file
reread .bashrc file using source command

source .bashrc

Write a program in java: 
Open your favorite editor in Linux. Type a sample Hello world program 
/*
java Hello World example.
*/
class HelloWorldExample 
{ 
public static void main(String args[]) 
{ 
/* 
Use System.out.println() to print on console. 
*/ 
System.out.println("Hello World !"); 
} 
} 
/* 
OUTPUT of the above given Java Hello World Example would be : 
Hello World ! 
*/ 
Save it as HelloWorldExample.java
Now compile it

javac HelloWorldExample.java

it will create a file named HelloWorldExample.class. Now you can run the HelloWorldExample.class file.

java HelloWorldExample

*** Important!!!!! this is HelloWorldExample not HelloWorldExample.class