Top 15+ Advanced Java Interview Questions

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Java is everywhere! Data shows that – it is the top choice for DevOps, VR, AI, Big Data, Analytics, Continuous Integration, Chatbots, Mobile apps, and Social media. And guess what? Major tech companies in India like – Accenture, Wipro, TCS, Amazon, and HCL, often include advanced Java questions in their interviews. So, to help you prepare – we’ve put together this guide with the top 15+ advanced Java interview questions and answers.

Let’s get started!

Advanced Java Interview Questions for Freshers

Here are the commonly asked advance Java interview questions for freshers and their answers. 

1. Can you explain the concept of Java Reflection?

Java Reflection is a feature that allows you to inspect and modify the runtime behaviour of applications. You can use it to examine classes, methods, and fields at runtime or even change their values. It’s useful for debugging or when working with unknown classes.

2. What is the difference between HashMap and TreeMap?

HashMap is faster for most operations because it uses hashing to store keys, which allows quick access. It does not maintain any order. TreeMap, on the other hand, stores keys in sorted order, so it is slower but useful when you need the keys to be sorted.

3. Explain the concept of Java Generics.

Java Generics allows you to create classes, interfaces, and methods that can operate on different types of data while providing compile-time type safety. 

4. What is the use of transient keyword in Java?

The transient keyword is used to mark a variable as not serializable. When an object is serialized, transient variables are not included in the serialized representation. This is useful when you have sensitive information that you don’t want to be serialized.

5. What is the use of garbage collection in Java?

Garbage collection in Java is used to automatically manage memory by reclaiming memory from objects that are no longer in use. This helps to prevent memory leaks and guarantees that the application does not run out of memory by freeing up space used by objects that are no longer needed.

6. How does Java handle memory management?

Java uses automatic memory management through garbage collection. The Java Virtual Machine (JVM) automatically reclaims memory used by objects that are no longer reachable or used by the program. This helps avoid memory leaks and manage memory efficiently.

Advanced Core Java Interview Questions

These are some important Core Java interview questions advanced and their answers.

7. Explain the concept of Java Serialization.

Java Serialization is the process of converting an object into a byte stream, allowing it to be saved to a file or transferred over a network. This byte stream can later be converted back into the original object using deserialization. It’s commonly used in scenarios like saving the state of an object or sending it between different parts of a distributed application.

8. What are static methods and variables in Java?

Static methods and variables belong to the class itself rather than to any specific instance of the class. This means you can call a static method or access a static variable without creating an instance of the class. They are shared among all instances of the class.

9. What is the purpose of the final keyword in Java?

The final keyword is used to define constants, prevent method overriding, and stop inheritance. When you declare a variable as final, its value cannot be changed. If a method is final, it cannot be overridden by subclasses. If a class is final, it cannot be subclassed.

Also Read - Top 15+ Inheritance in Java Interview Questions With Answers

10. How does Java handle exceptions?

Java handles exceptions through try, catch, finally, and throw. The try block contains code that might throw an exception, catch handles the exception and finally executes code regardless of whether an exception occurred. The throw statement is used to explicitly throw an exception.

11. What is the difference between ArrayList and LinkedList in Java?

ArrayList uses a dynamic array to store elements, which provides fast access to elements but slow insertion and deletion, especially in the middle of the list. LinkedList, on the other hand, uses a doubly-linked list structure, which allows for fast insertions and deletions at any position but slower access to elements compared to ArrayList.

Also Read - Top 20 Array Interview Questions In Java

Advanced Java Interview Questions for Experienced Candidates

Here are some important advance Java interview questions and answers for experienced candidates. 

12. What are Java Streams, and how are they used?

Java Streams, introduced in Java 8, are a powerful API for processing sequences of data. They allow operations like filtering, mapping, and reducing in a functional style, making code more concise and readable. For example, you can use streams to filter a list of objects based on certain criteria.

Also Read - Top 35+ Java 8 Interview Questions With Answers

13. When and how a deadlock occurs in any program?

A deadlock occurs when two or more threads are blocked forever, each waiting on the other to release a resource. This typically happens when multiple threads acquire locks in different orders. For example, if Thread A locks Resource 1 and waits for Resource 2, while Thread B locks Resource 2 and waits for Resource 1, both threads will be stuck indefinitely.

14. What are Lambda Expressions?

Lambda expressions in Java provide a way to write anonymous methods more concisely. They are primarily used to define the behaviour of functional interfaces (interfaces with a single abstract method). Lambda expressions enable writing cleaner and more expressive code, especially when working with collections and streams.

Also Read - Top 20+ Java Collections Interview Questions With Answers

15. Explain the concept of Java’s memory model.

Java’s memory model specifies how the Java Virtual Machine (JVM) handles memory and synchronization across threads. It ensures visibility and ordering of variables between threads, meaning changes made by one thread are visible to others. The volatile keyword is part of this model, ensuring that updates to a variable are immediately visible to all threads.

16. How does Java handle synchronization, and what are the common pitfalls?

Java handles synchronization using the synchronized keyword and Lock objects to manage access to shared resources in a multi-threaded environment. Common pitfalls include deadlocks and performance bottlenecks due to excessive synchronization, which can lead to reduced application throughput.

17. What is the role of the volatile keyword in thread safety?

The volatile keyword ensures that a variable’s value is always read from the main memory and not cached by a thread. This guarantees that changes to the variable by one thread are visible to all other threads, which is crucial in multi-threaded programming for ensuring data consistency.

Also Read - Top 25+ Core Java Interview Questions

Advanced Java Programming Questions

Here are the commonly asked advanced Java programming questions and answers. 

18. How do you create a custom exception in Java?

To create a custom exception, you extend the Exception class or one of its subclasses. 

For example:

public class MyCustomException extends Exception {

    public MyCustomException(String message) {

        super(message);

    }

}

You can then throw this exception in your code and catch it in your exception handling blocks.

19. Implement a method to find the longest common prefix of an array of strings.

public class LongestCommonPrefix {

    public static String longestCommonPrefix(String[] strs) {

        if (strs == null || strs.length == 0) {

            return “”;

        }

        String prefix = strs[0];

        for (int i = 1; i < strs.length; i++) {

            while (strs[i].indexOf(prefix) != 0) {

                prefix = prefix.substring(0, prefix.length() – 1);

                if (prefix.isEmpty()) {

                    return “”;

                }

            }

        }

        return prefix;

    }

    public static void main(String[] args) {

        String[] strs = {“flower”, “flow”, “flight”};

        System.out.println(longestCommonPrefix(strs)); // Output: “fl”

    }

}

Also Read - Top 25+ Interview Questions On String in Java with Answers

20. Write a method to check if two strings are anagrams of each other.

import java.util.Arrays;

public class AnagramChecker {

    public static boolean areAnagrams(String str1, String str2) {

        if (str1.length() != str2.length()) {

            return false;

        }

        char[] arr1 = str1.toCharArray();

        char[] arr2 = str2.toCharArray();

        Arrays.sort(arr1);

        Arrays.sort(arr2);

        return Arrays.equals(arr1, arr2);

    }

    public static void main(String[] args) {

        String str1 = “listen”;

        String str2 = “silent”;

        System.out.println(areAnagrams(str1, str2)); // Output: true

    }

}

21. Implement a method to find the nth Fibonacci number.

public class Fibonacci {

    public static int fibonacci(int n) {

        if (n <= 1) {

            return n;

        }

        int a = 0, b = 1, c;

        for (int i = 2; i <= n; i++) {

            c = a + b;

            a = b;

            b = c;

        }

        return b;

    }

    public static void main(String[] args) {

        int n = 7;

        System.out.println(fibonacci(n)); // Output: 13

    }

}

Also Read - Top 25+ Java Data Structures Interview Questions With Answers

Advance Java Viva Questions

These are some adv Java interview questions that you may come across in viva.

22. What is the difference between == and .equals() in Java?

The == operator checks if two references point to the same object in memory. It compares the memory addresses. The .equals() method checks if two objects are logically equivalent based on their content. By default, .equals() uses ==, but it can be overridden to compare the contents of objects.

23. What are the different types of inner classes in Java?

Java supports several types of inner classes:

• Non-static nested classes (Inner Classes): These have access to the enclosing class’s instance variables and methods.
• Static nested classes: These are similar to regular classes but are nested within another class. They do not have access to the enclosing class’s instance variables or methods.
• Local classes: These are defined within a method and can access local variables of the method if they are final or effectively final.
• Anonymous classes: These are nameless classes defined at the point of instantiation and used to create instances of classes or interfaces.

24. What is the purpose of the finalize() method in Java?

The finalize() method is called by the garbage collector before an object’s memory is reclaimed. It allows an object to perform cleanup actions, such as releasing resources or closing connections, before it is destroyed. However, relying on finalize() is discouraged in favour of try-with-resources and explicit resource management.

Also Read - Top 20+ Interview Questions On Java Servlets

Advanced Java MCQs

Here are some advanced Java important questions in MCQ form and their answers. 

25. Which of the following keywords is used to prevent a class from being subclassed?

A) final

B) static

C) abstract

D) private

Answer: A) final

26. What will be the output of the following code?

String str1 = “hello”;

String str2 = “hello”;

System.out.println(str1 == str2);

A) true

B) false

C) null

D) Compilation Error

Answer: A) true

27. What does the synchronized keyword do in Java?

A) Ensures a method can be executed by only one thread at a time

B) Makes a method thread-safe

C) Prevents a method from being overridden

D) Both A and B

Answer: D) Both A and B

28. Which collection class uses a hash table?

A) ArrayList

B) LinkedList

C) HashMap

D) TreeSet

Answer: C) HashMap

Also Read - Top 20+ HashMap Interview Questions With Answers

29.  What is the result of the following code snippet?

int a = 10;

int b = 20;

System.out.println(a++ + ++b);

A) 30

B) 31

C) 32

D) 33

Answer: B) 31

30. What is the default value of a boolean variable in Java?

A) true

B) false

C) 0

D) null

Answer: B) false

Also Read - Top 20+ Java Full Stack Developer Interview Questions With Answers

Wrapping Up

Understanding advanced Java concepts is essential for securing top tech jobs in India. These 15+ advanced Java interview questions and answers should help you prepare for your interview. Just stay confident and keep practising.And hey – if you are still on the hunt for tech jobs, visit Hirist. It is the best IT job portal in India. Simply install the Hirist app and find your dream job on the go.