LCM Example in Java

Introduction

LCM 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 least common multiple (also called the lowest common multiple or smallest common multiple) of two integers a and b, usually denoted by LCM(a, b), is the smallest positive integer that is divisible by both a and b. Since division of integers by zero is undefined, this definition has meaning only if a and b are both different from zero.

LCM Example Program

import java.util.Scanner;
 
public class LCM{
	public static void main(String[] args){
	Scanner in= new Scanner(System.in);
	System.out.print("Enter the num1:");
	int num1 =in.nextInt();
	System.out.print("Enter the num2:");
	int num2 =in.nextInt();
	int lcm = (num2 == num1 || num2 == 1) ? num1 :(num1 == 1 ? num2 : 0);
		if (lcm == 0) {
			int num3 = num1, num4 = num2;
			while (num3 != num4) {
				while (num3 < num4) { 
					num3 += num1; 
				}
				while (num4 < num3) { 
					num4 += num2;
				}
			}  
			lcm = num3;
		}
		System.out.println("lcm(" + num1 + ", " + num2 + ") = " + lcm);
	}
}

Sample Output

Enter the num1:66
Enter the num2:33
lcm(66, 33) = 66

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. The if statement runs the nested code only when the condition is true.

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.