Top 10 Tricky Interview Questions for Java Developers


Here is a list of top ten (10) tricky / popular interview questions and answers for Java developers. I got these questions out from Stackoverflow. You are a Junior or Intermidiate level Java developer and planning to appear for Java developer interviews in near future, you would find these questions to be useful enough.

Q1Is Java “pass-by-reference” or “pass-by-value”?

Ans: Java is always “pass by value”. Read the details on this page, Is Java “pass-by-reference” or “pass-by-value”?

Q2How to create a memory leak in Java?

Ans: This is possible by making use of Class loader and ThreadLocal. Read the details on this page, Creating a memory leak in Java

Q3What is difference between package private, public, protected, and private?

Ans: A private member variable is accessible within the same class; Package private variable (member variable with no access specifier) is accessible within all classes in the same package; A protected variable is accessible within all classes in the same package and within subclasses in other packages; A public member is accessible to all classes. Read greater details on this page

Q4Tell two differences between HashMap and a Hashtable?

Ans: Hashtable is synchronized; Hashtable does not allow null keys or values. Read greater details on this page, differences between HashMap and Hashtable

Q5What are different techniques of avoid != null statements (Not Null Check)?

Ans: Usage of assert statement is one of the ways; Custom annotations can be defined for NotNull checks; Read greater details on this page, How to avoid != null Statement.

Q6Does “finally” always execute in Java?

Ans: Not in the scenario such as invocation of “System.exit()” function, infinite loop or system crash etc; Read greater details on this page, Does finally always execute in Java

Q7Is it possible to call one constructor from another in Java?

Ans: Yes one can only chain to one constructor, and it has to be the first statement in your constructor body. Greater details can be found on this page, How do I call one constructor from another in Java?

Q8Which one should be used, “implements Runnable” vs. “extends Thread”?

Ans: Looks like “implements Runnable” is the preferred way. Read further details on this page, Implements Runnable vs Extends Thread

Q9Is it possible to break out of nested loops in Java?

Ans: Yes; Breaking out of nested loops in Java

Q10What is reflection and why is it useful?

Ans: Reflection is used to describe code which is able to inspect other code in the same system. Read reasons on this page, Why Reflection is useful.

Ajitesh Kumar

Ajitesh Kumar

Ajitesh is passionate about various different technologies including programming languages such as Java/JEE, Javascript, PHP, C/C++, mobile programming languages etc, and, computing fundamentals related with cloud-native technologies, application security, cloud computing platforms, mobile apps, big data etc.

He has also authored the book, Building Web Apps with Spring 5 and Angular.
Ajitesh Kumar

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