Top 10 Java Interview Questions for 2 to 3 years experience - Answered

Java Interview Questions 2 to 4 years of experience

If you are a Java programmer with 2 to 3 years experience of working in Java and looking for a job change then it's better to know what is expected from 2 to 3 years experienced Java programmer in a typical core Java or J2EE interview. Since 2 to 3 years is not a vast experience and you still fall under beginner to the intermediate category, it's not expected from you to have done profiling, Garbage collection tuning, designing complex Java applications, or even creating concurrent Java design patterns. 

What is expected from a 2 to 4 years experience guy in Java programming is a sound knowledge of Java fundamentals including OOPS concepts like Abstraction, Encapsulation, Polymorphism, Composition, and Inheritance, a good understanding of Java collection API, and familiarity with different kinds of collections like List, Set and Map with some familiarity with popular Collection classes e.g. ArrayList, HashMap, Vector, and HashSet, etc?

Fundamental knowledge of Java threading API, the wait-notify mechanism, and Exception handling in Java is also something the Interviewer look at in an intermediate Java programmer and of course some basic at programming and coding exercise like finding the length of a linked list in one pass or reversing String in Java, etc. 

If you manage to prepare these topics well, you are most likely to do well in Java interviews on service-based companies e.g. Tech Mahindra, Capgemini, CTS, Wipro, TCS, etc.

In this Java interview question and answer article, we will see some popular and tricky Java questions asked with 2 to 3 or 4 years experienced Java developers in software developer interviews.

But, if you are new to the Java world then I highly recommend you to check out The Complete Java Masterclass course to fill the gaps in your learning. This 80-hour long course is the best and most up-to-date course to learn Java. 

Top 10 Java Interview Questions 2 to 4 years of experience

Without wasting any more of your time, here is the list of top 10 Java interview questions for 2 to 4 years of experience programmers:

Question 1. What is the difference between Vector and ArrayList in Java?

Answer: One of the most popular Java questions at 2 years experience level which aims to check your knowledge on Java collection API. a key point to mention is synchronization and speed since ArrayList is not synchronized fast compared to Vector. See Vector vs ArrayList in Java for more differences between both of them.

Question 2. What is the difference between LinkedList and ArrayList in Java?

Answer: If you don't get a previous Java question then you are likely to get this question at 2 to 3 years experience level Java interview. Unlike synchronization, the key point to mention here is the underlying data structure. See LinkedList vs ArrayList in Java for a detailed answer to this java question.

3. What is the difference between fail-fast and fail-safe Iterator in Java?

This is a relatively new Java question compared to previous ones but increasingly getting popular in 2 to 3 years level Java interviews. the key difference here is that fail-fast Iterator throws ConcurrentModificationException while fail-safe doesn't. See fail-safe vs fail-fast Iterator in Java for more differences between the two.

4. Difference between throw and throws in Java?

This Java question belongs to the Exception handling category which is another popular category for 2 to 4 years experienced Java programmers. The main difference between these two is that one declares exceptions thrown by a Java method while the other is actually used to throw Exceptions. See the Difference between throw and throws in Java for a full answer to this Java exception handling question.

5. What is the difference between checked and Unchecked Exceptions in Java.

Another java interview question for 2 to 4 years experienced Java programmer from Exception handling. the key point to mention here is that checked Exception requires mandatory exception handling code while unchecked doesn't. See checked vs unchecked Exception in Java for more differences.

6. Write code to print the Fibonacci series in Java?

You are bound to expect some coding interview questions in Java interviews for 2 to 4 years of experience. Though the Fibonacci series is one of the most classical and popular questions, not every Java programmer is able to do it correctly in the interview, things get more complicated if the interviewer asks to do this by using recursion. So better to prepare for approach, See how to write a Java program for the Fibonacci series using recursion for details and code examples.

7. Write a Java program to reverse String in Java without using StringBuffer?

Another Java coding interview question asked on 2 to 4 years of experience in Java development. Many times interviewer specifically mentioned that you can not use StringBuffer because it has a reverse() method which makes these tasks trivial. So you must know how to do this by using iteration as well as recursion to perform well. Look at the Java program to reverse String in Java for a full code sample and explanation.

8. What is the difference between Runnable and Thread in Java?

Frequently asked Java interview questions on 2 to 4 years experience level from Threading fundamentals. there are two ways to implementing Thread in Java, in fact, three e..g extending java.lang.Thread class or implementing java.lang.Runnable or Callable interface. See Thread vs Runnable in Java for exact differences in following each approach.

9. What happens if you don't call wait and notify from the synchronized block?

Another common Java interview question is from multi-threading and inter-thread communication. As I said earlier you must know the concept of wait and notify in Java if you have worked for 2 to 3 years in Java. Check why wait and notify needs to call from a synchronized block for the exact reason to answer this Java question.

10. Write code to solve the producer-consumer problem in Java.

A good java question in my opinion is a mix of threading, synchronization, inter-thread communication, and coding abilities. This particular java question can make anybody's list on any day, not just 2 to 4 years of an experienced programmer. despite being so common it has something on it which confuses the average programmer and allows you to differentiate between good and average programmer. See Producer consumer problem solving using BlockingQueue in Java for a full code example.

These were 10 frequently asked Core Java interview questions for 2 to 3 years experienced Java programmers. If you want to increase numbers there are a lot many questions floating around the web for 2 to 3 or 2 to 4 years experienced Java developers but key things it to remember topics like Collection, Exception handling, Coding, Threading, and OOPS principles are the main areas from which most of 2 to 3 years of experience Java programmer interview questions appears. Just get them right and you can crack any Java interview up to 2 to 4 years experienced Java programmer.

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