Top 10 tricky Java interview questions and answers
Tricky Java interview questions are those question which has some surprise element on it and if you answer tricky Java question with common sense, you are likely to fail because they are tricky, they require something special to know. Most of the tricky Java questions comes from method overloading and overriding, Checked and Unchecked Exception and subtle Java programming details like Integer overflow. Most important thing to answer tricky Java question is attitude and analytical thinking , which helps even if you don't know the answer. Anyway in this Java article we will see 10 Java questions which is real tricky and requires more than average knowledge of Java programming language to answer. As per my experience there are always one or two tricky or tough Java interview question on any core Java or J2EE interviews, so its good to prepare tricky questions from Java in advance.
Tricky Java interview questions are those question which has some surprise element on it and if you answer tricky Java question with common sense, you are likely to fail because they are tricky, they require something special to know. Most of the tricky Java questions comes from method overloading and overriding, Checked and Unchecked Exception and subtle Java programming details like Integer overflow. Most important thing to answer tricky Java question is attitude and analytical thinking , which helps even if you don't know the answer. Anyway in this Java article we will see 10 Java questions which is real tricky and requires more than average knowledge of Java programming language to answer. As per my experience there are always one or two tricky or tough Java interview question on any core Java or J2EE interviews, so its good to prepare tricky questions from Java in advance.
10 Tricky Java interview question - Answered
Here is my list of 10 tricky Java interview questions, Though I have prepared and shared lot of difficult core java interview question and answers, But I have chosen them as Top 10 tricky questions because you can not guess answers of this tricky java questions easily, you need some subtle details of Java programming language to answer these questions.What will happen if you call return statement or System.exit on try or catch block ? will finally block execute?
This is a very popular tricky Java question and its tricky because many programmer think that finally block always executed. This question challenge that concept by putting return statement in try or catch block or calling System.exit from try or catch block. Answer of this tricky question in Java is that finally block will execute even if you put return statement in try block or catch block but finally block won't run if you call System.exit form try or catch.
Can you override private or static method in Java ?
Another popular Java tricky question, As I said method overriding is a good topic to ask trick questions in Java. Anyway, you can not override private or static method in Java, if you create similar method with same return type and same method arguments that's called method hiding. See Can you override private method in Java or more details.
Does Java support multiple inheritance ?
This is the trickiest question in Java, if C++ can support direct multiple inheritance than why not Java is the argument Interviewer often give. See Why multiple inheritance is not supported in Java to answer this tricky Java question.
What will happen if we put a key object in a HashMap which is already there ?
This tricky Java questions is part of How HashMap works in Java, which is also a popular topic to create confusing and tricky question in Java. well if you put the same key again than it will replace the old mapping because HashMap doesn't allow duplicate keys. See How HashMap works in Java for more tricky Java questions from HashMap.
If a method throws NullPointerException in super class, can we override it with a method which throws RuntimeException?
One more tricky Java questions from overloading and overriding concept. Answer is you can very well throw super class of RuntimeException in overridden method but you can not do same if its checked Exception. See Rules of method overriding in Java for more details.
What is the issue with following implementation of compareTo() method in Java
public int compareTo(Object o){
Employee emp = (Employee) emp;
return this.id - o.id;
}
where id is an integer number ?
Well three is nothing wrong in this Java question until you guarantee that id is always positive. This Java question becomes tricky when you can not guaranteed id is positive or negative. If id is negative than subtraction may overflow and produce incorrect result. See How to override compareTo method in Java for complete answer of this Java tricky question for experienced programmer.
How do you ensure that N thread can access N resources without deadlock
If you are not well versed in writing multi-threading code then this is real tricky question for you. This Java question can be tricky even for experienced and senior programmer, who are not really exposed to deadlock and race conditions. Key point here is order, if you acquire resources in a particular order and release resources in reverse order you can prevent deadlock. See how to avoid deadlock in Java for a sample code example.
What is difference between CyclicBarrier and CountDownLatch in Java
Relatively newer Java tricky question, only been introduced form Java 5. Main difference between both of them is that you can reuse CyclicBarrier even if Barrier is broken but you can not reuse CountDownLatch in Java. See CyclicBarrier vs CountDownLatch in Java for more differences.
What is difference between StringBuffer and StringBuilder in Java ?
Classic Java questions which some people thing tricky and some consider very easy. StringBuilder in Java is introduced in Java 5 and only difference between both of them is that Stringbuffer methods are synchronized while StringBuilder is non synchronized. See StringBuilder vs StringBuffer for more differences.
Can you access non static variable in static context?
Another tricky Java question from Java fundamentals. No you can not access static variable in non static context in Java. Read why you can not access non-static variable from static method to learn more about this tricky Java questions.
This was my list of 10 most common tricky question in Java . It's not a bad idea to prepare tricky Java question before appearing for any core Java or J2EE interview. One or two open ended or tricky question is quite common in Java interviews.
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Great questions, How about adding tricky questions related to programming exercise ?
ReplyDeleteGood work done! It will definitely help me in my interviews... :)
ReplyDeletethanks .. :)
Hi ,
ReplyDeleteI am able to override public static method declared in base class in its subclass.
It didn't throw any compilation or runtime exception
It won't because compiler will treat it as different method. This is called method hiding and its indeed one of the tricky Java question. Remember that this method is not overriding super class method as static method bonded using type information. That's the reason this Java question is tricky.
DeleteOne of the tricky Java question I faced is "What is difference between Collection and Generics in Java", its not tricky because I don't know either collection or Generics but How can you compare Generics with Collection ?
ReplyDeleteHi
ReplyDeleteIs the line in codes correct.
It's one of ur question.
Can you access non static variable in static context?
Another tricky Java question from Java fundamentals. "No you can not access static variable in non static context in Java". Read why you can not access non-static variable from static method to learn more about this tricky Java questions.
Hi Ankur, Thanks for pointing out, you should read opposite i.e non static variable can not accessible from static context. This always confuse if you don't remember it and that's why its one of the tricky question.
DeleteHi
DeleteThis line is not correct.
"No you can not access static variable in non static context in Java".
all are tricky questions?
ReplyDeleteits really nice tricky question to read to face interview.
ReplyDeletethese are not tricky rather easy questions ...
ReplyDeletei agree nice question to prepare before appearing for interview
ReplyDeleteThese are definitely a good set of tricky questions that a candidate may face during an interview. I certainly enjoyed going through them but I have a different opinion regarding the last question: Can you access non static variable in static context?
ReplyDeleteI think the answer to that question is a YES albeit one should note that you need an object reference of the associated class to access the variable (I assume this variable is an instance variable). And likewise you can directly access a static variable in non static context too. Please refer to this link for more information http://docs.oracle.com/javase/tutorial/java/javaOO/classvars.html
This very nice. It is very helpfull for me. Here I found More like Ths
ReplyDeleteJava Interview Questions and Answer
Is the compareTo code correct ? the references look to be wrong.
ReplyDeleteThe explanation of the last question is little bit confusing. Actually static variables are always accessible in non static context however the reverse is not true.
ReplyDeletepublic int compareTo(Object o){
ReplyDeleteEmployee emp = (Employee) emp;
return this.id - o.id;
}
I think this is what it should be...
public int compareTo(Object o){
Employee emp = (Employee) o;
return this.id - o.id;
}
Wrong, it should be:
Deletepublic int compareTo(Object o){
Employee emp = (Employee) o;
return this.id - emp.id;
}
Try some more new
ReplyDeletevery informative and good collection thanks for sharing
ReplyDeleteQ 1. about try and catch block
ReplyDeleteclass Main
{
public static void main(String args[])
{
try
{
int a=2/0;
System.exit(0);
}
catch(Exception e)
{
System.out.println("i am in catch block");
}
finally
{
System.out.println("finally");
}
}
}
/*OUTPUT
i am in catch block
finally*/
finally block get executed if we place System.exit(0) in try block
Before calling System.exit(0) you raised excetion "int a=2/0".
DeleteOnces system.exit(0) is called finally will never called.
plz Don't confused others :)
I was asked during an interview the difference between "arraylist" and "linkedlist" and when I should use them
ReplyDeleteAlso, found a site where you can give online Java mock interviews. Its www.preparestreet.com
these questions are really helped me to understand the concept, you can check Answer your Core Java OOPS Interview Questions . Well and simple way of explanation.
ReplyDelete