GCD Example in Java

Introduction

GCD is a classic Java console program that demonstrates the concept with complete source code and sample output. Calculation programs apply formulas to solve geometry, statistics and numeric problems.

This tutorial walks through the program line by line, explains how the logic works, and highlights best practices you can apply in your own code.

Definition

The greatest common divisor (gcd) of two or more integers, when at least one of them is not zero, is the largest positive integer that divides the numbers without a remainder.

GCD Example Program

import java.util.Scanner;
public class GCD {
    public static void main(String args[]){
        Scanner in = new Scanner(System.in);
        System.out.println("enter first number");
        int num1 = in.nextInt();
        System.out.println("enter second number");
        int num2 = in.nextInt();
        System.out.println("GCD of the given two numbers " + num1 +" and " + num2 +" is :" + findGCD(num1,num2));  
    }
    private static int findGCD(int num1, int num2) {
        if(num2 == 0){
            return num1;
        }
        return findGCD(num2, num1%num2);
    }
}

Sample Output

enter first number
56
enter second number
77
GCD of the given two numbers 56 and 77 is :7

When to use

Use these formulas in homework tools, engineering calculators or anywhere repeated numeric computation is needed.

How it works

1. Execution begins in the main method — the JVM calls this method when you run the class.

2. import java.util.Scanner; imports a class used later in the program.

3. A Scanner reads typed input from the keyboard (System.in).

4. A println / print call writes text to the console — part of the sample output below.

5. int num1 = in.nextInt(); updates a variable used in the calculation or output.

6. A println / print call writes text to the console — part of the sample output below.

7. int num2 = in.nextInt(); updates a variable used in the calculation or output.

8. A println / print call writes text to the console — part of the sample output below.

Best Practices

• Use meaningful variable and class names that describe their purpose.
• Compile and run the program locally — modify values to see how output changes.
• Read compiler errors carefully; they usually point to the exact line to fix.

Common Mistakes

• Copying code without understanding each line — practice by changing one statement at a time.
• Mismatching the public class name and the .java filename.
• Forgetting semicolons at the end of statements.