Java Interview Questions

Java Basics – Interview Questions and Answers


49. If I want an object of my class to be thrown as an exception object, what should I do?

The class should extend from Exception class. Or you can extend your class from some more precise exception type also.

50. If my class already extends from some other class what should I do if I want an instance of my class to be thrown as an exception object?

One can not do anytihng in this scenarion. Because Java does not allow multiple inheritance and does not provide any exception interface as well.

51. How does an exception permeate through the code?

An unhandled exception moves up the method stack in search of a matching When an exception is thrown from a code which is wrapped in a try block followed by one or more catch blocks, a search is made for matching catch block. If a matching type is found then that block will be invoked. If a matching type is not found then the exception moves up the method stack and reaches the caller method.

Same procedure is repeated if the caller method is included in a try catch block. This process continues until a catch block handling the appropriate type of exception is found. If it does not find such a block then finally the program terminates.

52. What are the different ways to handle exceptions?

There are two ways to handle exceptions,

1. By wrapping the desired code in a try block followed by a catch block to catch the exceptions. and

2. List the desired exceptions in the throws clause of the method and let the caller of the method hadle those exceptions.

53. Is it necessary that each try block must be followed by a catch block?

It is not necessary that each try block must be followed by a catch block. It should be followed by either a catch block or a finally block. And whatever exceptions are likely to be thrown should be declared in the throws clause of the method.

54. If I write return at the end of the try block, will the finally block still execute?

Yes even if you write return as the last statement in the try block and no exception occurs, the finally block will execute. The finally block will execute and then the control return.