Question

Write a method that determines if a given non-negative integer is a prime number, use the following method header: public static boolean isprime(int n) Prime numbers are integers that are divisible only by 1 and themselves; for example, 2, 5, 7, and 13 are prime numbers, while 15, 16, and 20 are not. By definition, 0 and 1 are not prime numbers. To test your method, write a simple program that asks the user to enter a number and then calls isprime to determine whether that number is prime (and displays an appropriate message). HINT: Be sure to test your program with 0, 1, and 2, as well as a large prime and a large non-prime. You can find lists of prime numbers on the Internet.

Answer 1

import java.util.Scanner;

public class Prime {

    public static boolean isprime(int n) {
        for (int i = 2; i < n; i++) {
            if (n % i == 0) {
                return false;
            }
        }
        return n > 1;
    }

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        System.out.print("Enter a number: ");
        int n = in.nextInt();
        if (isprime(n)) {
            System.out.println(n + " is a prime number");
        } else {
            System.out.println(n + " is NOT a prime number");
        }
    }
}