Best Practices - Quiz

Convert a string variable userInput to all uppercase letters before logging it.

Add a constant timeout value to a HashMap in a clear, self-documenting way.

Safely retrieve a value from an Optional<String> named email, providing a default if missing.

According to Java coding standards, which is the best name for a constant representing a maximum file size?

Which method name best follows clean code and Effective Java naming guidelines for a method that returns the total price?

Which principle from clean code is most closely related to keeping functions small and focused?

You want a flexible way to add logging behavior to a class without changing its inheritance hierarchy. Which approach is recommended?

Which situation most commonly leads to a NullPointerException in Java?

You frequently add and remove elements in the middle of a list. Which Java collection is generally more efficient?

What is the main benefit of writing unit tests before refactoring code?

In JUnit 5, which annotation marks a method as a test case?

Which practice helps most when debugging a complex issue?

Which statement about performance optimization is most aligned with best practices?

Which JUnit assertion is best to verify that a method throws an IllegalArgumentException?

Order the steps to create and use a JUnit 5 test for a Calculator class.

Drag and drop to reorder, or use the arrows.

Order the steps to debug a failing unit test in an IDE.

Drag and drop to reorder, or use the arrows.

What is the output of this code related to clean code naming?

1public class NamingExample {
2    public static void main(String[] args) {
3        int itemCount = 3;
4        int totalItems = itemCount + 2;
5        System.out.println(totalItems);
6    }
7}

What is the output of this code using composition?

1class Logger {
2    private final String name;
3    Logger(String name) { this.name = name; }
4    String format(String msg) { return name + ":" + msg; }
5}
6class Service {
7    private final Logger logger = new Logger("Service");
8    String start() { return logger.format("started"); }
9}
10public class Main {
11    public static void main(String[] args) {
12        Service service = new Service();
13        System.out.println(service.start());
14    }
15}

What is the output of this code demonstrating Optional to avoid NullPointerException?

1import java.util.Optional;
2public class OptionalDemo {
3    public static void main(String[] args) {
4        Optional<String> name = Optional.ofNullable(null);
5        String result = name.orElse("guest");
6        System.out.println(result);
7    }
8}

What is the output of this JUnit assertion-like logic?

1public class AssertLike {
2    private static boolean equals(int expected, int actual) {
3        return expected == actual;
4    }
5    public static void main(String[] args) {
6        boolean passed = equals(4, 2 + 2);
7        System.out.println(passed ? "PASS" : "FAIL");
8    }
9}

Find the bug related to null handling in this code.

Click on the line(s) that contain the bug.

public class UserService {

    public String getUserName(User user) {

        return user.getName().toUpperCase();

    }

}

class User {

    private final String name;

    User(String name) { this.name = name; }

    String getName() { return name; }

}

Find the performance-related bug in this string-building code.

Click on the line(s) that contain the bug.

public class ReportBuilder {

    public String buildReport(int n) {

        String report = "";

        for (int i = 0; i < n; i++) {

            report = report + "line" + i + ";";

        }

        return report;

    }

}

Match each Java testing concept with its description.

Click an item on the left, then click its match on the right. Click a matched item to unmatch.

Match each debugging tool action with what it does.

Click an item on the left, then click its match on the right. Click a matched item to unmatch.

Complete the code to define a clean, testable service using composition.

Complete the JUnit 5 test to verify that dividing by zero throws an exception.

Complete the code to iterate over a list of orders and calculate the total price cleanly.

Complete the code to measure response time for a method call.

Click the line that will cause a NullPointerException when this code runs.

Click on the line to select.

public class DebugHotspot {

    public static void main(String[] args) {

        String value = null;

        String trimmed = value.trim();

        System.out.println(trimmed);

    }

}

Click the line that is likely the performance bottleneck due to inefficient collection choice.

Click on the line to select.

import java.util.ArrayList;

import java.util.List;

public class PerformanceHotspot {

    public static void main(String[] args) {

        List<Integer> numbers = new ArrayList<>();

        for (int i = 0; i < 100000; i++) {

            numbers.add(i);

        }

        numbers.add(0, -1);

        System.out.println(numbers.size());

    }

}