Check Prime Number
Aim :
Check if the given number is prime or not.
Important Definition:
Prime Number : A number is prime if it is divisible of itself and 1, otherwise not.
1 is not prime number.
For Example:
n = 17
It is prime as no any number in set of [2, 16] divides 17 and give reminder 0.
n = 21
It is not prime as 3 divides 21 which is in [2, 20].
Code:
package com.BasicsOfJava;
import java.util.Scanner;
public class CheckPrime {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
System.out.print("Enter the number :" );
int n = in.nextInt();
boolean isPrime = prime( n);
if( isPrime) {
System.out.println("Prime " );
}
else {
System.out.println("NotPrime");
}
}
// This are the efficient methods we can also do is check for all the number from 2 to N
// but after chekcing square root is just waste of time for you and computer too. whala 🤣.
static boolean prime(int n ) {
if( n <= 1) {
return false;
}
int c= 2;
while( c*c <= n) {
if( n%c == 0) {
return false;
}
c++;
}
return c * c > n;
}
// this is method for prime number checking
// static boolean prime(int n) {
// for(int i=2; i*i <=n ; i++) {
// if( n %i == 0 ) {
// return false;
// }
// }
// return true;
// }
}