Here is a java program to check, whether a number is prime number or not. We have to check whether given number is prime number or not. First of all, we have to understand fundamentals of prime numbers.
- A Prime number is a positive number greater than 1 that is only divisible by either 1 or itself.
- All numbers other than prime numbers are known as composite numbers.
- Any non-prime number can be expressed as a factor of prime numbers.
- There are infinitely many prime numbers, here is the list of first few prime numbers
2 3 5 7 11 13 17 19 23 29 31 37....
Java program to check for prime number
Let N be the number for primality testing. Here, we will use brute force approach by testing whether N is a multiple of any integer between 2 and N/2. This is the most basic method of checking the primality of a given integer N and is called trial division method.
package com.tcc.java.programs;
import java.util.*;
public class PrimeNumberCheck {
public static void main(String args[]) {
int num, i, isPrime = 0;
Scanner in = new Scanner(System.in);
System.out.println("Enter an Integer");
num = in.nextInt();
for(i = 2; i <= (num / 2); ++i) {
if (num % i == 0) {
isPrime = 1;
break;
}
}
if (isPrime == 0)
System.out.println(num + " is a Prime Number");
else
System.out.println(num + " is not a Prime Number");
}
}
Output
Enter an Integer 23 23 is a Prime Number
Enter an Integer 30 30 is not a Prime Number
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