Catching and Handling Exceptions

Start of Tutorial > Start of Trail > Start of Lesson Lesson Contents

Trail:
Essential Java Classes

Lesson:
Handling Errors with Exceptions

Help on searching
is available.
Search technology
by Excite, Inc.

Catching and Handling Exceptions
Now that you've familiarized yourself with the ListOfNumbers class and where the exceptions can be thrown within it, you can learn how to write exception handlers to catch and handle those exceptions.
The three sections that follow cover the three components of an exception handler -- the try, catch, and finally blocks. They show you how to write an exception handler for the ListOfNumbers class's writeList method, described in The ListOfNumbers Example. Next, you'll walk through the resulting writeList method and see what occurs within the example code during various scenarios.
The try Block

The first step in writing an exception handler is to enclose the statements that might throw an exception within a try block. The try block is said to govern the statements enclosed within it and defines the scope of any exception handlers (established by subsequent catch blocks) associated with it.

The catch Block(s)

Next, you associate exception handlers with a try block by providing one or more catch blocks directly after the try block.

The finally Block

Java's finally block provides a mechanism that allows your method to clean up after itself regardless of what happens within the try block. Use the finally block to close files or release other system resources.

Putting It All Together

The previous sections describe how to construct the try, catch, and finally code blocks for the writeList example. Now, let's walk through the code and investigate what happens during three scenarios.

Start of Tutorial > Start of Trail > Start of Lesson Lesson Contents