30/12/24
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Q)Which software executes a Java program?
=>Java Virtual Machine(JVM)

Q)What is the entry point of a Java program?
 =>Program's execution starts from which part, that part is known as
 the entry point of the Java program.
 =>main method is the entry point of a Java program.

 Q)Explain about the following program.
1 class HelloWorld{
2     public static void main(String args[]){
3          System.out.println("Hello World !");
4     }
5 }

Program's Explanation
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1:- class declaration+class definition/body starts
      =>"class" is a keyword in Java.
      =>"HelloWorld" is the name of the class.
      =>HelloWorld class is used to encapsulate main method.
2:- main method header+main method definition starts.
3:- main method is calling the println method.
4:- main method definition ends/main method body ends
5:- class definition ends.
6:- main method definition ends

Q)How to display data on the console(Monitor) in a Java application?
=>by using println method.

Q)Why is main method declared public?
 =>To give access permission to the JVM to call the main method, it is
 declared public .

Q)Why is main method declared static?  
=>to fecilitate the JVM to call the main method without the need of creating 
the object of the class.

Q)Explain about portability of Java applications.
   =>The ability of a program to run even if its source code is moved from
   one type of machine to the other type of machine.

Q)What is byte code?
  =>byte code is not machine code.
  =>".class" file contains byte code.
  =>Intermediatory instructions that are understadable to any JVM
  is nothing but byte code.

Q)Explain about OS(Platform) independency of Java applications.
=>The ability of a Java program to run in any machine even if it is moved
from one machine to another machine after compilation.
=>Three things contribute to the Platform independency of
Java applications.
   1)Java compiler
   2)OS dependent JVM
   3)class file format

=>In any Operating system environment, Java compiler creates
the same class file.

=>class file contains byte code which is understandable
to any kind of JVM.

=>JVM is OS dependent. It translates the class file content into underlying operating system
understandable machine code to be given to the processor.