Question

Exception handling All Exceptions that can be thrown must descend from this Java class: The getMessage( ) method is inherited from this class? What are the two broad catagories of Exceptions in Java? If an Exception is not a checked exception it must extend what class? What is the difference between a checked Exception and an unchecked Exception? What are the two options a programmer has when writing code that may cause a checked Exception to be thrown? Can a try block contain code that would cause more than one type of Exception to possibly be thrown? Is it true that a try block can only be followed by ONE catch block? What is the purpose of the finally block? When is the code in the finally block executed? What happens when a try block throws an Exception object? Is an Exception the same thing as a syntax or logic error?

Answer 1

(a) Throwable class is the superclass from which all exceptions are derived.

(b) There are two types of exceptions in Java - Checked exceptions and unchecked excpetions.

(c) Unchecked exceptions extend either the Error class or the RuntimeException class.

(d) Checked exceptions are checked at compile time whereas unchecked exceptions are not.

(e) If a programmer is writing code that may cause a checked exception to be thrown, his method must either handle the exception or he must declare the exception using the throws keyword.

(f) Yes, a try block can have code that can cause more than one exception to be thrown.

(g) No, a try block can be followed by multiple catch blocks. Like so,

try{
         // Some code here
     }
     catch(ArithmeticException e){
        //
     }
     catch(ArrayIndexOutOfBoundsException e){
        //
     }
     catch(Exception e){
        //
     }

(h) The purpose of the finally block is to contain all those statements that have to be executed irrespective of whether an exception occurs or not.

(i) If there is no exception, then the code in the finally block is executed after the execution of the try block. However, if an exception occurs then the finally block is executed after the execution of the catch block.

(j) When a try block throws an exception it is caught by its corresponding catch block.

(k) An Exception can be caught by the program and handled accordingly. The same is not true for an Error. Errors are unchecked Exceptions.