Classes and Objects

System.out.println

• prinln: Prints in aline/prints wih line break
• Print: Prints without line break

System - Class Out - Object of system println - method in out

Multiline comment

 /*
									This is a comment
								 */
								 //  Single line comment
								

JDK for developer JRE for platform

JDK is rhe suoerset if JR MCQS

• 1. Source to byte bhy JVM
• 1. All The above
• 1. Multi Threading

Reuse of same class

Variables

• Local
• Public

Variable inside a class is member Varibale inside a method is Local Varible

• Member varible

  • Instance Variable

    • Created when onject of class
    • Multiple copies

  • Static Variable

    • Has single copy
    • If varable is staic all other methods will share the same memory

package com;
								public class HelloClass {
								
									static String name = "Object one";
								
									public static void main(String[] args) {
										// TODO Auto-generated method stub
										System.out.println("My Name is "+args[0]);
										System.out.println("Phone Number "+args[1]);
										System.out.println("City : "+ args[2]);
										System.out.println("Length of My Name : "+args[0].length());
										System.out.println("Uppercase of My Name : "+args[0].toUpperCase());
								
										// Variable Class
								
										HelloClass obj = new HelloClass();
										HelloClass obj2 = new HelloClass();
										System.out.println(obj.name);
										System.out.println(obj2.name);
										obj.name = "Object 2";
										System.out.println(obj.name);
										System.out.println(obj2.name);
										}
								
								}
								

Local Variable only accesable within a method itself

There are several kinds of variables:

• Member variables in a class—these are called fields.
• Variables in a method or block of code—these are called local variables.

• Variables in method declarations—these are called parameters.

• Local variable must be initialized before use

Switch

package com;
								
								public class HelloClass {    
									public static void main(String args[]) {
										for(int i=0; i<=4; i++)
										switch(i) {
										case 0:
										System.out.println("i is zero."); break;
										case 1:
										System.out.println("i is one."); break;
										case 2:
										System.out.println("i is two."); break;
										case 3:
										System.out.println("i is three."); break;
										default:
										System.out.println("i is greater than 3.");
										}
								
										}
								
								}
								

package day2ex;
								import java.util.*;
								public class Hello {
								
								static int sumOfDigits(int number){
									int sum = 0;
									int cubes = 0;
									while(number !=0) {
										sum = number%10;
										cubes += sum*sum*sum;
										number/=10;
									}
									return cubes;
								}
								
								public static void main(String[] args)  
									{  
									Scanner sc= new Scanner(System.in); 
									//Create a method to find the sum of the cubes of the digits of an n digit number
									System.out.print("Enter  number- ");  
									int a= sc.nextInt();   
								
									System.out.println("Total= " + sumOfDigits(a) );  
									}
								}