Java - Exception Handling Interview Questions

What will happen if you put System.exit(0) on try or catch block?

In normal Finally block will always execute. The only case finally block is not executed is System.exit(0). In advanced case it will execute in following case.

By Calling System.exit(0) in try or catch block, its stops execution & throws SecurityException.

·         If System.exit(0) NOT throws security exception, then finally block Won’t be executed

·         But, if System.exit(0) throws security exception then finally block will be executed.

java.lang.System.exit() will terminates the currently executing program by JVM.

·         exit(0) : Generally used to indicate successful termination.

·         exit(1) or exit(-1) or any other non-zero value –indicates unsuccessful termination.

What happens if we put return statement on try/catch? Will finally block execute?

Yes, finally block will execute even if you put a return statement in the try block or catch block.

try {

    //try block

    ...

    return success;

}

catch (Exception ex) {

    //catch block

    .....

    return failure;

}

finally {

    System.out.println("Inside finally");

}

The answer is yes. finally block will execute. The only case where it will not execute is when it encounters System.exit().

What happens when a finally block has a return statement?

Finally block overrides the value returned by try and catch blocks.

public static int myTestingFuncn(){

  try{

     ....

     return 5;

  }

  finally {

     ....

     return 19;

   }

}

This program would return value 19 since the value returned by try has been overridden by finally.

Why do you think Checked Exception exists in Java, since we can also convey error using RuntimeException?
Most of checked exceptions are in java.io package, which make sense because if you request any system resource and its not available, than a robust program must be able to handle that situation gracefully.

By declaring IOException as checked Exception, Java ensures that your provide that gracefully exception handling. Another possible reason could be to ensuring that system resources like file descriptors, which are limited in numbers, should be released as soon as you are done with that using catch or finally block
 

Have you faced OutOfMemoryError in Java? How did you solved that?
OutOfMemoryError in Java is a subclass of java.lang.VirtualMachineError and JVM throws java.lang.OutOfMemoryError when it ran out of memory in the heap.

An easy way to solve OutOfMemoryError in java is to increase the maximum heap size by using JVM options "-Xmx512M", this will immediately solve your OutOfMemoryError.

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