17/12/24
---------
Q)How to develop and run a Java program?
DIAGRAM

Step 1:- Write the program code (Source code)

Step 2:- Save the source code(source file creation)
             =>We can give any name to the Java source file. But, its extension
	     should be ".java".
	        For eg.    addition.java

Step 3:- Compile the source code


Step 4:- Execute/Run the Java program


Q)Java program to display Hello World ! on the console.
class HelloWorld{
    public static void main(String a[]){
         System.out.println("Hello World !");  
    }
}
Q)How to compile a Java program?
=>By using "javac" command.

                javac   <source file>
     For eg.
                javac one.java
Q)What happens in the background when "javac" command is executed?
   =>"javac" command is given to the Operating System.
   =>OS invokes the Java compiler.
   =>Java compiler does the following things.
            1)Makes a full read of the source code of the source file
            2)verifies the syntactical correctness of the source code
	        Case i:- Errors are there
		=>Compiler reports those errors and it doesn't perform
		compilation(translation)

                 Case ii:- No errors are found

		 =>Java compiler translates Java source code into byte code
		 and it creates one or more class files.
Note:- Java compiler creates as many .class files as there are classes in the
source code
Q)How to run a Java program?
=>by using "java" command.
       java <Initial class Name>

  For eg.   java HelloWorld

Note:- Initial class is that class in which, main method is defined.

Q)What happens in the background when "java" command is executed?
=>"java" command is given to the OS.
=>OS invokes the JVM
=>JVM does the following things.
      1)Loads the initial class (class file) into RAM
      2)Calls the main method and the program's execution starts.