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Prime number program in java

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In this example you will learn how to write a program to generate and check prime number in java.

Prime number program in java

In this example you will learn how to write a program to generate and check  prime number  in java. As we know prime number are those number which are divisible by 1 or itself, first define a class with class name prime number, using switch case, in case first using two for loop generating prime number up to the limit number entered by user and in second case checking whether the entered number is prime number or not.

Example : Here is the code for generating prime number and to check the prime number.

import java.io.*;
import java.util.Scanner;
 class Primenumber 
 {
 public static void main(String args[])throws Exception
 {
 char st;
 Scanner sin,stc;
 String c;
 do
 {
 System.out.println("Press 1 for generate prime number");
 System.out.println("Press 2 for check prime number ");
 sin=new Scanner(System.in);
 int s=sin.nextInt();
 switch(s)
 {
   case 1:System.out.println("Enter the limit number");
          int limit = new Scanner(System.in).nextInt();
          System.out.println("Printing prime number from 1 to " + limit);
          for(int number = 2; number<=limit; number++){
             //print prime numbers only
          if(Primegen(number)){
          System.out.println(number);}}
          break;
  
   case 2: int n, i, res;
          boolean flag=true;
          Scanner scan= new Scanner(System.in);
          System.out.println("Please Enter a No.");
          n=scan.nextInt();
          for(i=2;i<=n/2;i++)
           {
             res=n%i;
             if(res==0)
             {
               flag=false;
               break;
              }
            }
              if(flag)
                 System.out.println(n + " is Prime Number");
              else
                 System.out.println(n + " is not Prime Number");
             break;

   default:  System.out.println("Not Valid option"); 
             break;
          }

         System.out.println("Do u want to Execute again(Y/N)");
         stc=new Scanner(System.in);
         c=stc.next();
         st=c.charAt(0);
         } while(st!='N');
            }
          public static boolean Primegen(int number){
          for(int i=2; i<number; i++){
          if(number%i == 0){
            return false;           //number is divisible so its not prime
          }
      }
           return true; 
      }
}

Output : After Compiling and executing the above program.

Download SourceCode

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Posted on: May 24, 2013

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