Best Way to Calculate GCD in Java for Primitive Types

General Discussions
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What is the best way to calculate GCD in Java?

I know that BigInteger has a built-in gcd method (BigInteger#gcd), but I was wondering if there are similar functions in Java that work for int, long, or Integer types. It feels like something that should be in java.lang.Math, but I couldn’t find it there.

How can I efficiently compute the Greatest Common Divisor (GCD) in Java for primitive types like int and long? Is there a built-in method, or do I need to implement it manually?

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In case you’re okay with using BigInteger, this method is one of the easiest ways to calculate java gcd for large numbers. Here’s how you can use it:

import java.math.BigInteger;

public class GCDExample {
    public static void main(String[] args) {
        int a = 36, b = 60;
        BigInteger bigA = BigInteger.valueOf(a);
        BigInteger bigB = BigInteger.valueOf(b);

        int gcd = bigA.gcd(bigB).intValue();
        System.out.println("GCD using BigInteger: " + gcd);
    }
}

:white_check_mark: Why use this? If you’re dealing with larger numbers, BigInteger is the built-in solution for computing java gcd.

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If you prefer to stick with primitive types like int or long, and want to avoid the overhead of BigInteger, you can easily implement the java gcd using the classic Euclidean algorithm. Here’s how:

public class GCDRecursive {
    public static int gcd(int a, int b) {
        return (b == 0) ? a : gcd(b, a % b);
    }

    public static void main(String[] args) {
        System.out.println("GCD using recursion: " + gcd(36, 60));
    }
}

:white_check_mark: Why use this? This approach is fast, elegant, and works great for typical java gcd calculations with small to medium-sized integers. It’s a classic for a reason!

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If you’re worried about the depth of recursion or prefer a more performance-optimized solution, consider using an iterative approach to calculate java gcd. This avoids any recursion limit issues:

public class GCDIterative {
    public static int gcd(int a, int b) {
        while (b != 0) {
            int temp = b;
            b = a % b;
            a = temp;
        }
        return a;
    }

    public static void main(String[] args) {
        System.out.println("GCD using iteration: " + gcd(36, 60));
    }
}

:white_check_mark: Why use this? This method is iterative, avoids deep recursion calls, and tends to perform faster, especially when dealing with larger inputs, ensuring reliable java gcd calculations for all use cases.