Compilation

• javac Prog_Name.java
• Output : Prog_Name.class (bytecode file)

Execution

• java Prog_Name

Structure

class Prog_Name
{
  public static void main(String args[]) 
  {
    ....
  }
}

public : main() should be able to be called by the JVM i.e the code outside the class.
static : main() would have to be called by JVM before creating an instance of the class containing it.

Comments

Multiline : /* for multiple line comments */  
Singleline : // single line comment
Documentation : /** used to produce an HTML file that documents your program */

Misc

• There are 50 keywords in JAVA.
• true,false,null are reserved apart from the 50 keywords.
• JAVA is a strongly typed language , meaning , variables have data types and type compatibility is checked before assigning the value of an expression to a variable.