3/1/25
--------
Q)JDK Vs JRE Vs JVM

DIAGRAM

Q)How are Java platforms classified?
1)Java SE (Standard Edition Of Java)+stand-alone applications
2)Java EE(Java Enterprise Edition )=>web applications
3)Java ME(Java Micro Edition)=>Mobile applications
Q)On which cycle does a  Computer Application run?
=>IPO(Input   Process  Output)
Q)How to read data from the keyboard in a Java program?
  =>by using the library methods of Scanner class.

Q)Java program to perform the addition of two numbers interactively.
//InteractiveAddition.java
import java.util.Scanner;
class InteractiveAddition{
    public static void main(String args[]){
           Scanner scanner=new Scanner(System.in);
	       System.out.print("Enter the first number:");
	       int n1=scanner.nextInt();
	       System.out.print("Enter the second number:");
	       int n2=scanner.nextInt();
	       int sum=n1+n2;
           System.out.println("The sum is "+sum);
    }//main
}//class
=>In the above program we have used 4 Java classes.
=>InteractiveAddition is the user defined class(our own created class).
=>Scanner,String and System are library classes(pre-defined classes)
=>Scanner class belongs to java.util package.
=>System & String belong to java.lang package. For every
Java program, java.lang package is automcatically(implicitly) available.Therefore
we need not import String & System classes.

Q)What are the similarities between print() and println()?
  =>Both are library methods.
  =>Both are used to display data on the monitor in Java program.

Q)What is the difference between print() and println()?
=>println() method prints a blank line after printing the data.
Where as print doesn't.
Q)What is a local variable?
    =>A variable declared inside a vmethod is known as a local variable.

Q)What is the output of the following Java application?
class Output{
    public static void main(String args[]){
        int a;
        System.out.println(a);
    }
}

Ans:- The above program causes compilation error.
Reason:- Using a local variable without initializing it is syntactical error in Java.

Q)What is a comment in a Java application?
=>Textual description of the Java application written
within the source code which is ignored by the compiler
is nothing but a comment.
=>We have 2 types of implementation comments.
      1)single line comment
      2)multi-line comment
=>Single line comment starts with "//" and ends with the physical line
=>Multi-line comment starts with "/*" and ends with "*/".

For eg.
/*
    This application is developed on 3-01-25
    by AshokIt team.

*/
class Output{
    public static void main(String args[]){
        int a;//local variable
        int sum=a+10;//using a local variable
    }
}
Q)What is a data type?
=>data type is a one that specifies the kind of data that can be
stored in computer's memory

Q)How are data types classified in Java?
       1)primitive/pre-defined/system-defined/fundamental/basic data types
       2)user defined data types
Q)What are the primitive data types in Java?
=>There are 8 primitive data types in Java.
   
   1)byte
   2)short
   3)int
   4)long

   5)float
   6)double

   7)char
   8)boolean