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Interview Questions and Answers for 'Exception' - 82 question(s) found - Order By Rating

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Q1. Can we pass the junit test if the tested method throws the exception ? and Should we do that ?

Ans. Yes, We can pass the test even if the tested method throws an exception.

One way is know as exception testing in which the tested method is expected to throw exception and hence the expectation is set accordingly.

@Test(expected = IndexOutOfBoundsException.class)
public void test(){}

Other way is to just ignore if the tested code throws an exception. In that case , we can enclose the tested method call in the try block and within exception block, we just return gracefully.

Exception testing is perfectly ok to be done as we would like test code in case an exception occurs and if the code is handling the exception properly. Ignoring the exception by putting the tested method call within try block isn't something normal and should be avoided.

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_{Like Discuss Correct / Improve Junit exception testing}

Q2. What is Throwable ?

Ans. Throwable in java is a class that is the superclass of all exceptions and errors which may occurs in java program.It extends obcect class.

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_{Like Discuss Correct / Improve exception handling throwable Asked in 1 Companies basic}

Q3. If we have a return statement inside the finally block, Then what will happen ?

Ans. Returning from inside a finally block will cause exceptions to be lost. A return statement inside a finally block will cause any exception that might be thrown in the try block to be discarded.

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_{Like Discuss Correct / Improve exception handling finally block Asked in 1 Companies}

Q4. Explain CloneNotSupportedException ?

Ans. If we do not mention, Cloneable Interface to the Class which we want to Clone then we get this exception, only if we try to clone an object

Like:
public class TestClone{
@Override
   protected Object clone() throws CloneNotSupportedException {
      return super.clone();
   }
}

In Main, You try to do:
TestClone clone = new TestClone();

      TestClone clone2 = (TestClone) clone.clone();

You will get CloneNotSupportedException.

Just add -> public class TestClone implements Cloneable {

and things are fixed.

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_{Like Discuss Correct / Improve exceptions handling cloning}

Q5. What is the difference between try-catch and @ExceptionHandler in Java/Spring Boot?

Ans. ExceptionHandler is Used to handle at Method level

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_{Like Discuss Correct / Improve @ExceptionHandler}

Q6. Differences between class not found exception and noclassdef found error ?

Ans. ClassNotFoundException is an exception that occurs when we try to load a class at run time using Class.forName() or loadClass() methods and mentioned classes are not found in the classpath.

NoClassDefFoundError is an error that occurs when a particular class is present at compile time, but was missing at run time.

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_{Like Discuss Correct / Improve exception handling ClassNotFoundException NoClassDefFoundError Asked in 1 Companies}

Q7. Will this give compile time error ?

Object[] strArray = new String[2];
strArray[0] = 5;

Ans. No. But It will throw ArrayStoreException at runtime.

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Q8. What is ArrayStoreException ?

Ans. It's an exception that is thrown when we attempt to add value of an incompatible type to an array.

For example -

Object[] strArray = new String[2];
strArray[0] = 5;

In this code, strArray reference of type Object has currently been assigned the String array but at line 2 we are trying to add an integer value.

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_{Like Discuss Correct / Improve arrays ArrayStoreException}

Q9. What is the difference between ArrayIndexOutOfBoundException and ArrayStoreException?

^{This question is still unanswered. Can you please provide an answer.}

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_{Like Discuss Correct / Improve exception handling}

Q10. What will happen if there is an exception in Java finally block ?

Ans. The regular behavior of exception handling will occur. It will look for any immediate catch handler and if none is provided, it would be transmitted to the callers until a catch handler is found or it's out of main function.

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Q11. Can you explain following exception

java.lang.ArithmeticException: Non-terminating decimal expansion; no exact representable decimal result.

^{This question is still unanswered. Can you please provide an answer.}

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_{Like Discuss Correct / Improve ArithmeticException}

Q12. Is it a bad practice to initialize object reference to Null ?

Ans. never initialise local to null,yes it is bad pratice

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_{Like Discuss Correct / Improve null nullpointerexception}

Q13. What is the purpose of re throwing the exception when we can provide the handling at the first catch itself ?

Ans. Sometimes the calls move across layers of classes and functions and hence each layer needs to perform some function like cleaning if something goes wrong deep inside.

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_{Like Discuss Correct / Improve exceptions exceptions handling rethrowing exception}

Q14. Can we catch errors in Java ?

Ans. Yes we can

try {
// code
} catch (Error ex) {
// handling code
}

but we shouldn't ideally do that as errors are mostly JVM based and not application based and there is rarely we can do something about it. Very likely catching and not re throwing would lead to muting their response or trace.

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_{Like Discuss Correct / Improve exception handling error handling errors Asked in 1 Companies intermediate}

Q15. Is it ok to use optional everywhere just to get over nullpointerexception ?

Ans. Optional is to be used for arguments / atrributes which are indeed optional i.e the request should continue even if they aren't provided. It should not be used for mandatory attributes or arguments as we would like application to shout out ( with error message / exception trace ) to signify a problem.

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_{Like Discuss Correct / Improve optional nullpointerexception java8 java 8 Asked in 1 Companies}

Q16. What will happen if we don't have termination statement in recursion ?

Ans. It would result in endless function calls and hence eventually would result in stackoverflow exception.

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_{Like Discuss Correct / Improve recursion stackoverflowexception Basic frequent}

Q17. What could be the possible cause for following exception ?

org.hibernate.StaleObjectStateException: Row was updated or deleted by another transaction (or unsaved-value mapping was incorrect):

What could be the way to fix it ?

Ans. This looks like the case for optimistic locking wherein hibernate suspects that the information in table was updated by some other transaction after the entity was loaded by current transaction.

One way is to have synchronized entity state and don't detach the entity. Other could be to merge the entity with the table record rather than just directly persisting the entity.

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_{Like Discuss Correct / Improve StaleObjectStateException Optimistic locking}

Q18. What is ConstraintViolationException in Hibernate ?

Ans. The exception is thrown when a database constraint is violated.

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Q19. What do you make out of this error

org.hibernate.exception.ConstraintViolationException: could not insert: [<Entity>]
Caused by: java.sql.SQLIntegrityConstraintViolationException: ORA-00001: unique constraint (<Constraint Name>) violated

and how would you go about debugging it ?

Ans. Application is unable to insert a record as it violates a unique constraint.

The exception states the constraint and Table can be located by the Entity mapping. So I will go to the DB and will first check to which all columns the unique constraint applies. And then I will go and check the code and logs to see how come the duplicate column values were attempted to be inserted when they were not supposed to be.

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_{Like Discuss Correct / Improve ConstraintViolationException SQLIntegrityConstraintViolationException}

Q20. Doesn't it make sense to necessarily initialize references to some object to avoid NullPointerExceptions ? Can this be done ?

Ans. We can declare the reference as final to avoid reassignment but again we can always initialize the final reference to null. Even if there was any such facility available , it would have meant poor use of resources by assigning a new object in memory to each reference that's created. Many a times references are just meant to refer to other objects which already have a reference i.e sharing object by multiple references.

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_{Like Discuss Correct / Improve null NullPointerException}

Q21. Is it advisable to keep session or transaction open for long time just to avoid LazyInitializationException ?

Ans. No. It's a resource and performance overhead.

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_{Like Discuss Correct / Improve LazyInitializationException Lazy Loading}

Q22. If you are given choice to avoid LazyInitializationException using any of the following measures, which are the ones you will choose and why ?

1. Set lazy=false in the hibernate config file.
2. Set @Basic(fetch=FetchType.EAGER) at the mapping.
3. Make sure that we are accessing the dependent objects before closing the session.
4. Force initialization using Hibernate.initialize

Ans. First resolution is a big No as it conveys no lazy loading in complete app. even second is advocating the same but for a particular mapping.

third one is most appropriate if loading and dependent entity property access is closer to each other in code and can be accomplished.

I don't mind using 4th too.

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_{Like Discuss Correct / Improve lazy loading lazy initialization LazyInitializationException}

Q23. What does the following exception means

org.hibernate.LazyInitializationException: could not initialize proxy - no Session

Ans. The error states that Hibernate is not able to initialize proxy / dependent entity objects as there is no session or transaction present. Very likely we are trying to load the dependent entities lazily but the call to dependent object property is not wrapped within the session or transaction.

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_{Like Discuss Correct / Improve Lazy Loading Lazy Initialization org.hibernate.LazyInitializationException}

Q24. What is Exception Wrapping ?

Ans. Exception wrapping is wrapping an exception object within another exception object and then throwing the outer exception.

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_{Like Discuss Correct / Improve exception handling exception wrapping exceptions intermediate rare}

Q25. Can we have only try block in java ?

Ans. No, It should be followed by either catch or finally.

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Q26. How should we handle errors while writing or accessing Stored Procedures?

Ans. Store Procedure returns the error code. Moreover we can put the call withing try block and catch SQL Exception.

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Q27. What are the different ways to handle an exception ?

Ans. 1. Wrap the desired code in try block followed by a catch / finally to catch the exception

2. Declare the throws clause with exceptions that the code is expected to throw as an indication to the calling method to take care of it.

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_{Like Discuss Correct / Improve exception handling Asked in 4 Companies}

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Q28. What is an exception and exception handling in Java ?

Ans. An Exception in java is the occurrence during computation that is anomalous and is not expected.

Exception handling is the mechanism which is used to handle such situations.

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_{Like Discuss Correct / Improve exception handling Asked in 18 Companies basic frequent}

Q29. When is the situation when finally section won't execute ?

Ans. If the process / app is abruptly killed or terminated.

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_{Like Discuss Correct / Improve exception handling finally Asked in 2 Companies intermediate}

Try 1 Question(s) Test

Q30. What is the difference between following code segments

1.

try {
for(int i=0;i<100;i++){
calculate(i);
}
} catch (Exception ex) {
System.out.println("Error while processing")
}

and

2.

for(int i=0;i<100;i++){
try {
calculate(i);
} catch (Exception ex) {
System.out.println("Error while processing")
}
}

Ans. In first case the whole loop will terminate as soon as any exception happens in the method calculate ( assuming calculate method is not handling its exception and those are thrown back at the calling method )

In Second case exception will be caught for individual iteration and hence it wont break the loop and will continue for the next iteration.

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_{Like Discuss Correct / Improve exception handling try catch Asked in 1 Companies}

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