Prime Number Program in Java

Here, first we understand that what is prime number,

Prime Numbers

A prime number is a natural number greater than 1, that is divisible by only two numbers: 1 and itself.

For Example: 2, 3, 5, 7,11,13……..are the prime numbers.

Note: 0 and 1 are not prime numbers.
The 2 is the only even prime number because all the other even numbers can be divided by 2.

Problem:

Input :   Enter a number: 17
Output:  17 is a prime number.

Explanation

This Java program checks if a given number is prime or not. It prompts the user for input, then utilizes a `for` loop to iterate from 2 up to the square root of the number. Within each iteration, it checks if the number is divisible by the current value of `i`. If a divisor is found, it concludes the number is not prime. If no divisors are found, then it’s a prime number.

Solution:

code:

class PrimeNo{
    public static void main(String []args){
        int num=7;
        int temp=0; 
        for(int i =2;i<=num-1;i++){
            if(num%i==0){
             temp=temp+1;
            }
        }
        if(temp==0){
            System.out.println(num+" is a prime number");
        }
        else{
            System.out.println(num+" is not prime number ");
        }
    }
}

Output:

7 is a prime number

Approach 2 : By Using Scanner Class :

import java.util.Scanner; // import scanner class
class PrimeNo{
    public static void main(String []args){
        Scanner sc =new Scanner(System.in);  // object of scanner class 
        int temp=0;
        System.out.println("enter any number");
        int num = sc.nextInt();
        for(int i =2;i<=num-1;i++){
            if(num%i==0){
             temp=temp+1;
            }
        }
        if(temp==0){
            System.out.println(num+" is a prime number");
        }
        else{
            System.out.println(num+" is not prime number ");
        }
    }
}

Output:

enter any number
77
77 is not prime number

more java programs for practice:

Java Program to Get Input from User

Find the Greatest of the Two Numbers in Java

Addition of two numbers in java