Prime number and prime numbers between a given range program in Java

Prime number in Java: Prime number is a number that is greater than 1 and divided by 1 or itself. In other words, prime numbers can't be divided by other numbers than itself or 1. For example 2, 3, 5, 7, 11, 13, 17.... are the prime numbers.

Let's see the prime number program in java. In this java program, we will take a number variable and check whether the number is prime or not.

1. class PrimeExample{  

1.  public static void main(String args[]){  

1.   int i,m=0,flag=0;    

1.   int n=17;//it is the number to be checked  

1.   m=n/2;    

1.   for(i=2;i<=m;i++){    

1.    if(n%i==0){    

1.    System.out.println("Number is not prime");    

1.    flag=1;    

1.    break;    

1.    }    

1.   }    

1.   if(flag==0)    

1.   System.out.println("Number is prime");    

1. }  

1. }  

Output:

Number is prime 

How to get the prime numbers between a given range.

package javaTutorial;

import java.util.ArrayList;
import java.util.Scanner;

public class GetPrimeNumbers{
    public static void main(String[] args){
        Scanner in = new Scanner(System.in);
        System.out.println("Enter a number from which you want prime number: ");
        int p1 = in.nextInt();
        System.out.println("Enter one more number till which you want prime number: ");
        int p2 = in.nextInt();
        ArrayList<Integer> prime = new ArrayList<Integer>();
        int i=2;
        for(int p=p1; p<=p2; p++){
            i=2;
            for(; i<10; i++){  
                if(p%i==0 && p!=i){
                    break;
                }
            }
            if(i==10){
                prime.add(p);
            }
        }
        System.out.println("Prime numbers between "+p1+" and "+p2+" are: ");
        for(int j=0; j<prime.size(); j++){
            System.out.print(prime.get(j).toString()+", ");
        }      
    }
}
 
Output:
 
Enter a number from which you want prime number:
10
Enter one more number till which you want prime number:
30
Prime numbers between 10 and 30 are:
11, 13, 17, 19, 23, 29,