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Java Program: Compare Two floats precisely (Epsilon-Based)

Why Epsilon Comparison?

Floating-point numbers may not be stored exactly in memory, so direct comparison using == can give incorrect results.
An epsilon-based comparison checks whether the difference between two numbers is small enough to be considered equal.

Java

import java.util.Scanner;
 
public class FloatComparison {
    public static void main(String[] args) {
 
        Scanner sc = new Scanner(System.in);
 
        System.out.print("Enter first floating-point number: ");
        double num1 = sc.nextDouble();
 
        System.out.print("Enter second floating-point number: ");
        double num2 = sc.nextDouble();
 
        // Define tolerance (epsilon)
        double epsilon = 0.000001;
 
        System.out.println("\n------ Float Comparison Result ------");
 
        if (Math.abs(num1 - num2) < epsilon) {
            System.out.println("Both numbers are approximately equal.");
        }
        else if (num1 > num2) {
            System.out.println("First number is greater than second number.");
        }
        else {
            System.out.println("Second number is greater than first number.");
        }
 
        sc.close();
    }
}

Output

 
OUTPUT 1:

INPUT : 
Enter first floating-point number: 0.3
Enter second floating-point number: 0.3000001

OUTPUT :
------ Float Comparison Result ------
Both numbers are approximately equal.

OUTPUT 2:
 
INPUT : 
Enter first floating-point number: 5.25
Enter second floating-point number: 5.10

OUTPUT :
------ Float Comparison Result ------
First number is greater than second number.

OUTPUT 3:
 
INPUT : 
Enter first floating-point number: 4.75
Enter second floating-point number: 4.90

OUTPUT :
------ Float Comparison Result ------
Second number is greater than first number.

Explanation

1. Input Two Floating-Point Numbers

double num1 = sc.nextDouble();

double num2 = sc.nextDouble();

Reads two decimal numbers from the user.

2. Epsilon Definition

double epsilon = 0.000001;

Represents the allowed tolerance for comparison.

3. Epsilon-Based Comparison

Math.abs(num1 - num2) < epsilon

Calculates the absolute difference between the two numbers.
If the difference is smaller than epsilon, they are treated as equal.

4. Logical Decision

if (...)

else if (...)

else

Determines equality, greater-than, or less-than.

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Java Program: Compare Two floats precisely (Epsilon-Based)

Output

Explanation