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.
Q1: Is 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”?
Q2: How 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
Q3: What 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
Q4: Tell 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
Q5: What 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.
Q6: Does “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
Q7: Is 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?
Q8: Which 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
Q9: Is it possible to break out of nested loops in Java?
Ans: Yes; Breaking out of nested loops in Java
Q10: What 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.
He has also authored the book, Building Web Apps with Spring 5 and Angular.
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