Unveiling the Top 10 Tricky Java Interview Questions and Answers

As a Java developer, landing your dream job often hinges on your ability to navigate through the trickiest of interview questions. Employers are constantly on the lookout for candidates who can think critically, analyze complex scenarios, and demonstrate a deep understanding of Java’s intricate concepts. In this article, we’ll explore the top 10 tricky Java interview questions and provide detailed answers to help you ace your next interview.

1. What will the following Java program print?

public class Test {    public static void main(String[] args) {        System.out.println(Math.min(Double.MIN_VALUE, 0.0d));    }}

Answer: This question is tricky because, unlike the Integer class, where the MIN_VALUE is negative, the Double class’s MIN_VALUE is the smallest positive non-zero value. The program will print 0.0 because Double.MIN_VALUE (approximately 4.9e-324) is greater than 0.0d.

2. What happens if you put a return statement or System.exit() in the try or catch block? Will the finally block execute?

Answer: The finally block will execute successfully if you put a return statement in the try or catch block. However, the finally block will fail to execute if you call System.exit() from the try or catch block because the JVM terminates immediately.

3. Can you override a private or static method in Java?

Answer: No, you cannot override a private method in Java because it is not accessible in the subclass. As a workaround, you can create a new private method with the same name in the child class.

Similarly, you cannot override a static method in Java. If you create an identical method with the same return type and method arguments in the child class, it will hide the superclass method. This is known as method hiding.

4. What will the expression 1.0 / 0.0 return? Will it throw an exception or any compile-time errors?

Answer: The expression 1.0 / 0.0 will compile successfully and not throw an ArithmeticException. Instead, it will return Double.POSITIVE_INFINITY.

5. Does Java support multiple inheritances?

Answer: Java does not allow multiple inheritances of implementation (classes). However, it supports multiple inheritances of type by enabling one interface to extend other interfaces. This means that a class can implement multiple interfaces, but it can only extend one class.

6. What happens if we put a key object in a HashMap that already exists?

Answer: HashMap does not allow duplicate keys. If you put the same key again, it will overwrite the original mapping. The new value will replace the old value associated with the existing key.

7. What does the following Java program print?

public class Test {    public static void main(String[] args) throws Exception {        char[] chars = new char[] {'u0097'};        String str = new String(chars);        byte[] bytes = str.getBytes();        System.out.println(Arrays.toString(bytes));    }}

Answer: This question is particularly tricky because the program’s output depends on the operating system and locale. On a Windows XP with the US locale, the program prints [63]. However, on Linux or Solaris, you may get different values.

8. If a method throws NullPointerException in the superclass, can we override it with a method that throws RuntimeException?

Answer: Yes, you can throw a superclass of RuntimeException (e.g., RuntimeException itself) in the overridden method, but you cannot do that if it’s a checked exception.

9. What is the difference between CyclicBarrier and CountDownLatch in Java?

Answer: The main difference is that you can reuse CyclicBarrier even if the barrier is broken, but you cannot reuse CountDownLatch in Java.

10. Can you access a non-static variable in the static context?

Answer: No, you cannot access a non-static variable from the static context in Java, as it will give a compile-time error. Static members can only access other static members directly.

By mastering these tricky Java interview questions and their answers, you’ll be better prepared to showcase your problem-solving skills and impress potential employers. Remember, interviews are not just about reciting facts; they’re also about demonstrating your ability to think critically and apply your knowledge to real-world scenarios.

Additional Tips for Java Interviews

Beyond these tricky questions, here are some additional tips to help you ace your Java interview:

• Review core Java concepts: Brush up on fundamental topics like object-oriented programming, data structures, algorithms, and Java Collections Framework.
• Practice coding: Solve coding problems on platforms like LeetCode, HackerRank, or CodeQuotient to sharpen your coding skills.
• Understand design patterns: Familiarize yourself with common design patterns like Singleton, Factory, Observer, and their real-world applications.
• Stay up-to-date: Keep yourself informed about the latest Java features, updates, and best practices.
• Prepare for behavioral questions: Be ready to discuss your experience, projects, and how you approach problem-solving.
• Ask questions: Don’t hesitate to ask clarifying questions during the interview if you’re unsure about something.

By combining a solid understanding of Java concepts, practical coding experience, and effective communication skills, you’ll be well-equipped to tackle even the trickiest of Java interview questions. Good luck with your job search!