Understanding how **floating point numbers** behave in Java is crucial when you work with calculations that require precision. Unlike **integers**, floating point numbers such as `float` and `double` are subject to rounding errors caused by the way computers represent decimal values in binary. This can lead to surprising results, especially when performing simple arithmetic like adding `0.1` and `0.2`.

To see this in action, you will write a small program that uses both `float` and `double` to add these two numbers and prints the results. Observing the output will help you recognize why **floating point arithmetic** can sometimes produce unexpected results and why you must be aware of these limitations when working with real-world data.

package com.example;

import static org.junit.jupiter.api.Assertions.*;

import org.junit.jupiter.api.DisplayName;
import org.junit.jupiter.api.Test;

public class MainTest {

    @Test
    @DisplayName("calculateSums() returns non-null array of length 2")
    void testCalculateSumsArrayStructure() {
        double[] results = Main.calculateSums();
        assertNotNull(results, "calculateSums() should not return null");
        assertEquals(2, results.length, "calculateSums() should return array of length 2");
    }

    @Test
    @DisplayName("First element (float sum) is close to 0.3f within delta")
    void testFloatSumAccuracy() {
        double[] results = Main.calculateSums();
        float expected = 0.3f;
        float actual = (float) results[0];
        float delta = 0.0001f;
        assertEquals(expected, actual, delta, "First element should be close to 0.3f (float sum)");
    }

    @Test
    @DisplayName("Second element (double sum) is close to 0.3 within small delta")
    void testDoubleSumAccuracy() {
        double[] results = Main.calculateSums();
        double expected = 0.3;
        double actual = results[1];
        double delta = 0.0000001;
        assertEquals(expected, actual, delta, "Second element should be close to 0.3 (double sum)");
    }
}


MainTest.java

A comprehensive course on Java data types, covering primitives, reference types, type conversion, and practical applications. Designed for learners with basic Java syntax knowledge.

Explore Java's built-in primitive data types, their properties, and how to use them effectively.

Delve into Java's reference types, focusing on Strings and arrays, and how they differ from primitives.

Learn about type casting, automatic conversions, and the use of wrapper classes for primitives.

Challenge: Floating Point Precision

Solução

Awesome!

Challenge: Floating Point Precision

Solução