HOWTO · Java
How to Check if a Number Is Prime in Java
This tutorial demonstrates how to check if a number is prime or not in Java.
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In Java, we can implement different methods to check if a number is prime or not.
This tutorial demonstrates different methods of checking if a number is prime or not.
Use while Loop to Check if a Number Is Prime in Java
You can use a while loop to develop a method to check if the input number is prime or not.
Example Code:
package delftstack;
import java.util.Scanner;
public class Is_Prime {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
System.out.println("Enter the number you want to check: ");
int Input_Number = sc.nextInt();
int temp = 2;
boolean condition = false;
while (temp <= Input_Number / 2) {
// condition to check for a non-prime number
if (Input_Number % temp == 0) {
condition = true;
break;
}
++temp;
}
if (!condition) {
System.out.println("The Number " + Input_Number + " is a prime number.");
} else {
System.out.println("The Number " + Input_Number + " is not a prime number.");
}
}
}
Output:
Enter the number you want to check:
11
The Number 11 is a prime number.
or
Enter the number you want to check:
90
The Number 90 is not a prime number.
Use the for Loop to Check if a Number Is Prime in Java
You can also utilize the for loop to create a method to check if the input number is prime or not.
Example Code:
package delftstack;
import java.util.Scanner;
public class Is_Prime {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
System.out.println("Enter the number you want to check: ");
int Input_Number = sc.nextInt();
boolean condition = false;
for (int x = 2; x <= Input_Number / 2; ++x) {
// condition to check for a non-prime number
if (Input_Number % x == 0) {
condition = true;
break;
}
}
if (!condition) {
System.out.println("The Number " + Input_Number + " is a prime number.");
} else {
System.out.println("The Number " + Input_Number + " is not a prime number.");
}
}
}
Output:
Enter the number you want to check:
3
The Number 3 is a prime number.
Create a Method to Check if a Number Is Prime in Java
We will create a method named isPrime() and use it to check if the input number is a prime or not.
Example Code:
package delftstack;
import java.util.Scanner;
public class Is_Prime {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
System.out.println("Enter the number you want to check: ");
int Input_Number = sc.nextInt();
if (isPrime(Input_Number)) {
System.out.println("The Number " + Input_Number + " is a prime number.");
} else {
System.out.println("The Number " + Input_Number + " is not a prime number.");
}
}
static boolean isPrime(int input_number) {
if (input_number <= 1) {
return false;
}
// check for a non-prime number
for (int x = 2; x < input_number; x++) {
if (input_number % x == 0) {
return false;
}
}
return true;
}
}
Output:
Enter the number you want to check:
10
The Number 10 is not a prime number.
