Java program to Find whether number is Prime or Not

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class PrimeNo{
	public static void main(String args[]){
		int num = Integer.parseInt(args[0]);
		int flag=0;
		for(int i=2;i<num;i++){
			if(num%i==0)
			{
				System.out.println(num+" is not a Prime Number");
				flag = 1;
				break;
			}
		}
		if(flag==0)
			System.out.println(num+" is a Prime Number");
	}
}

28 Responses to “Java program to Find whether number is Prime or Not”

  1. Suryansh Srivastava

    import java.util.*;
    class prime_number
    {
    static Scanner sc = new Scanner (System.in);
    public static void main()
    {
    System.out.print(“Enter A Number : “);
    int n=sc.nextInt();

    if(n==2)
    {
    System.out.println(“\n2 is a prime number”);
    }
    for(int i=2;i<n;i++)
    {
    if(n%i==0)
    {
    System.out.print("\n"+n+" is not a prime number");
    break;
    }
    else
    {
    System.out.print("\n"+n+" is a prime number");
    break;
    }
    }
    }
    }

    Reply
  2. Shetty Pramod

    the for loop should be continued only till n/2, because a number after this cannot divide n.

    Reply
  3. hariprasanth

    import java.util.*;
    import java.io.*;

    public class one
    {
    public static void main(String args[])
    {
    int num;
    int flag=0;
    System.out.println(“Enter an integer to check ?”);
    Scanner in = new Scanner(System.in);
    num = in.nextInt();

    for(int i=2;i<num;i++){
    if(num%i==0)
    {
    System.out.println(num+" is not a Prime Number");
    flag = 1;
    break;
    }
    }
    if(flag==0)
    System.out.println(num+" is a Prime Number");
    }
    }

    Reply
  4. why did you use the flag .why did you assign 0 and 1 in the flag.it is only comes under true or false statement.

    Reply

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