Here is everybody's favorite program in Java:

public class Hello {
  public static void main (String args[]) {
    System.out.println ("Hello, World!");
  }
}

To run this program,

1. Copy this program exactly as written onto a file named Hello.java. Do not give the file some other name.
2. Compile the file by putting it in the same directory as the compiler and issuing the command
       javac Hello.java
   This should create a file named Hello.class
3. Run the file by issuing the command
       java Hello
   This should print "Hello, World!"

Notes

• Java cares what file name you use. If your class is named Hello, then it must be in a file named Hello.java. If your operating system has case-sensitive file names, the first part of the file name (Hello in this case) must be capitalized the same way as in your program.
• The Java compiler javac requires the name of the file (as you would expect), that is, Hello.java.
• To execute the Java program, the java interpreter that wants the name of the class only, with no .class extension--given the class name, it can figure out the file name.