Java Program to Find GCD or HCF of Two Numbers - The Coding Shala

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 Hey there, welcome back to another post. In this post, we will learn how to find GCD or HCF of Two Numbers in Java.

Java Program to Find GCD or HCF of Two Numbers

The GCD (Greatest Common Divisor) or HCF (Highest Common Factor) of two numbers is the largest number that divides both of them. For example: 

Number1: 6 (2 * 3)
Number2: 9 (3 * 3)
GCD or HCF of 6 and 9 is: 3

Find GCD of Two Numbers in Java using for Loop

As we already know, GCD is the largest number that divides both numbers. We can start a for loop from 1 (because 1 divides all the numbers) to both numbers and if it divides both numbers then update GCD.

Java Program: 

import java.util.Scanner;

/**
 * https://www.thecodingshala.com/
 */

public class Main {

    public static void findGCD(int num1, int num2) {
        int gcd = 1;
        if (num1 == 0) {
            gcd = num2;
        }
        if (num2 == 0) {
            gcd = num1;
        }

        // find largest common divisor
        for (int i = 1; i <= num1 && i <= num2; i++) {
            if (num1%i == 0 && num2%i == 0) {
                gcd = i;
            }
        }

        System.out.println(gcd);
    }

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.println("Enter first number");
        int num1 = sc.nextInt();
        System.out.println("Enter second number");
        int num2 = sc.nextInt();

        System.out.println("GCD of " + num1 + " and " + num2 + " is:");
        findGCD(num1, num2);
    }
}

Output: 

Enter first number
36
Enter second number
60
GCD of 36 and 60 is:
12

Fing GCD of Two Numbers in Java using While Loop

We can find the HCF or GCD of two numbers using a while loop.

Java Program: 

import java.util.Scanner;

/**
 * https://www.thecodingshala.com/
 */

public class Main {

    public static void findGCD(int num1, int num2) {
        if (num1 == 0) {
            System.out.println(num2);
            return;
        }

        if (num2 == 0) {
            System.out.println(num1);
            return;
        }

        while (num1 != num2) {
            if (num1 > num2) {
                num1 = num1 - num2;
            } else {
                num2 = num2 - num1;
            }
        }

        System.out.println(num1);
    }

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.println("Enter first number");
        int num1 = sc.nextInt();
        System.out.println("Enter second number");
        int num2 = sc.nextInt();

        System.out.println("GCD of " + num1 + " and " + num2 + " is:");
        findGCD(num1, num2);
    }
}

Output: 

Enter first number
36
Enter second number
60
GCD of 36 and 60 is:
12


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