An exception is an event, which is not expected to occur in the normal operation

of a program. When an exceptional condition causes an exception to be thrown,

that exception is an object derived, either directly, or indirectly from the

class Throwable. The Throwable class has two subclasses:

    1. Error: An Error indicates that a non-recoverable error has occurred, that

       should not be caught. Errors usually cause the Java interpreter to display

       a message and exit.

    

    2. Exception: An Exception indicates an abnormal condition, that must be

       properly handled to prevent program termination. All exceptions other than

       those in the RuntimeException class must be either caught or declared.

       Exceptions can occur for many reasons, for example, dividing a number by

       zero; trying to access an array element which doesn't exist.

All errors and exceptions may have a message associated with them, which can be

accessed using the getMessage() method. You can use this method to display a

message, describing the error or exception.

Here is the general syntax of exception handling in Java:

    try 

    {

        //Code which might cause an exception

    } 

    catch(Exception e) 

    {

        //Exception handling code

    }

When an exception occurs in Java, an Object is created, which is of the Exception

type, this is then thrown, until it is caught. If an exception occurs in a Java

program and is left unhandled, the program will stop executing and the user will

see a runtime error. The following code generates such a runtime error by

attempting to access an array element, which doesn't exist.