In this challenge, you will apply your knowledge of `String.format()` to create a professional-looking receipt. Your goal is to implement a method called `formatReceipt` that takes three lists: item names, their quantities, and their prices. The method should return a formatted string that represents a receipt, with each item's name, quantity, and price displayed in neatly aligned columns. Prices must always display two decimal places for clarity. This exercise will help you master column alignment and numeric formatting, which are essential skills for producing readable console output in Java.

package com.example;

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

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

import java.util.Arrays;
import java.util.List;
import java.util.regex.Pattern;
import java.util.regex.Matcher;

public class MainTest {
    @Test
    @DisplayName("Header row contains correct labels")
    void testHeaderRow() {
        List<String> items = Arrays.asList("A");
        List<Integer> quantities = Arrays.asList(1);
        List<Double> prices = Arrays.asList(1.0);
        String receipt = com.example.Main.formatReceipt(items, quantities, prices);
        assertTrue(receipt.contains("Item") && receipt.contains("Quantity") && receipt.contains("Price"),
            "Header row should contain 'Item', 'Quantity', and 'Price' labels");
    }

    @Test
    @DisplayName("Separator row is directly below header")
    void testSeparatorRow() {
        List<String> items = Arrays.asList("A");
        List<Integer> quantities = Arrays.asList(1);
        List<Double> prices = Arrays.asList(1.0);
        String receipt = com.example.Main.formatReceipt(items, quantities, prices);
        String[] lines = receipt.split("\\\\r?\\\\n");
        assertTrue(lines.length >= 2, "Receipt should have at least two lines (header and separator)");
        assertTrue(lines[1].replaceAll("\\\\s+", "").matches("-+--+--+"),
            "Second line should be a separator row of dashes");
    }

    @Test
    @DisplayName("Each item is on its own line, columns aligned")
    void testItemRowsAlignment() {
        List<String> items = Arrays.asList("Apple", "Banana");
        List<Integer> quantities = Arrays.asList(2, 10);
        List<Double> prices = Arrays.asList(1.2, 2.5);
        String receipt = com.example.Main.formatReceipt(items, quantities, prices);
        String[] lines = receipt.split("\\\\r?\\\\n");
        assertTrue(lines.length >= 4, "Receipt should have header, separator, and one line per item");
        // Check alignment: item name left, quantity and price right
        String itemLine1 = lines[2];
        String itemLine2 = lines[3];
        assertTrue(itemLine1.startsWith("Apple"), "First item line should start with item name left-aligned");
        assertTrue(itemLine2.startsWith("Banana"), "Second item line should start with item name left-aligned");
        assertTrue(itemLine1.trim().matches("Apple\\\\s+2\\\\s+1.20"), "First item line columns formatted correctly");
        assertTrue(itemLine2.trim().matches("Banana\\\\s+10\\\\s+2.50"), "Second item line columns formatted correctly");
    }

    @Test
    @DisplayName("Prices always show two decimal places")
    void testPriceDecimalPlaces() {
        List<String> items = Arrays.asList("Eggs");
        List<Integer> quantities = Arrays.asList(1);
        List<Double> prices = Arrays.asList(2.0);
        String receipt = com.example.Main.formatReceipt(items, quantities, prices);
        Pattern p = Pattern.compile("\\\\d+\\\\.\\\\d{2}");
        Matcher m = p.matcher(receipt);
        boolean found = false;
        while (m.find()) {
            if (m.group().equals("2.00")) {
                found = true;
                break;
            }
        }
        assertTrue(found, "Price should be formatted with two decimal places (e.g., 2.00)");
    }

    @Test
    @DisplayName("Handles lists of equal length")
    void testEqualLengthLists() {
        List<String> items = Arrays.asList("A", "B", "C");
        List<Integer> quantities = Arrays.asList(1, 2, 3);
        List<Double> prices = Arrays.asList(1.0, 2.0, 3.0);
        String receipt = com.example.Main.formatReceipt(items, quantities, prices);
        String[] lines = receipt.split("\\\\r?\\\\n");
        assertEquals(5, lines.length, "Receipt should have 5 lines: header, separator, and 3 items");
    }
}

MainTest.java

Master the art of formatting and parsing data in Java, from string templates to numbers and dates, and learn how to create well-structured console tables. This course is designed for learners with a basic understanding of Java syntax who want to deepen their skills in data presentation and manipulation.

Explore the power of String.format() for dynamic and readable string construction in Java, including formatting numbers, aligning text, and embedding variables.

Delve into the DecimalFormat class for precise control over numeric output, including custom patterns, rounding, and parsing.

Master date parsing/formatting with LocalDate and DateTimeFormatter, and learn to create visually appealing tables in the console.

Challenge: Receipt Formatter

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Challenge: Receipt Formatter

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