Java Program to Check Prime Number - The Coding Shala

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 In this post, we will learn how to Check if a Given Number is a Prime Number or not in Java.

Java Program to Check Prime Number

A Prime Number is a number that is divisible by 1 and the number itself. For example, the number 5 is a Prime Number because it is divisible by 1 and 5 only. 

Note: Number 0 and 1 are not prime numbers.

Example 1:

Input: 7

Output: Prime Number

Example 2:

Input: 9

Output: Not a Prime Number

Java Program: 

// Java program to Check Prime Number

import java.util.Scanner;

public class Main {
	
	static boolean isPrime(int num) {
		if(num < 2) return false;
		
		//  basic for loop ==> for(int i = 2; i < num / 2; i++ )
		for(int i = 2; i * i <= num; i++) {
			if(num % i == 0) return false;
		}
		return true;
	}
	
	public static void main(String[] args) { 
		Scanner sc = new Scanner(System.in);
		
		// take input char
		System.out.println("Enter the Number: ");
		int num = sc.nextInt();
		
		if(isPrime(num)) {
			System.out.println(num + " is a Prime Number");
		} else {
			System.out.println(num + " is not a Prime Number");
		}
		
		sc.close();
	}
}

Output: 

Enter the Number: 
8
8 is not a Prime Number

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