isPrime.java

import java.util.Scanner;
import java.util.*;
import static java.lang.System.out;
public class Ques4 {
	public static void main(String[] Args) {
		Scanner in = new Scanner(System.in);
		int n, c;
		boolean ch;
		out.print("Enter Number: ");
		n = in.nextInt();
		ch = isPrime(n);
		if(ch) 
			out.println("is Prime!");
		else
			out.println("isn't Prime!");
		for(int i = 3; i <= n; i++) 
			if(isPrime(i)) 
				out.print(i + " ");
	}
	private static boolean isPrime(int num) {
		if (num == 2 ) return true;
		if (num % 2 == 0) return false;
		for (int i = 3; i * i <= num; i += 2)
		    if (num % i == 0) return false;
		return true;
	}
}