Baldwin discusses and illustrates many of the details having to do with exception handling in Java.
Revised: Fri Apr 01 18:00:56 CDT 2016
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Table of contents
Preface
This module is one of a series of modules designed to teach you about Object-Oriented Programming (OOP) using Java.
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Figure 1 . Throwable constructors.
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Figure 2 . Methods of the Throwable class.
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Figure 3 . Compiler error from an unhandled checked exception.
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Figure 4 . Another compiler error.
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Figure 5 . Output from program that throws ArithmeticException.
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Figure 6 . Syntax of a try block.
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Figure 7 . Syntax of a catch block.
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Figure 8 . Output produced by the finally block.
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Figure 9 . Syntax for declaring that a method throws exceptions.
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Figure 10 . Example of a throw statement.
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Figure 11 . Output from the for loop.
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Figure 12 . Output from the exception handler.
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Figure 13 . Output from code following the catch block.
Listings
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Listing 1 . Sample program with no exception handling code.
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Listing 2 . Sample program that fixes one compiler error.
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Listing 3 . Sample program that fixes the remaining compiler error.
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Listing 4 . A sample program that throws an exception.
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Listing 5 . The power of the finally block.
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Listing 6 . The class named MyException.
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Listing 7 . The try block.
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Listing 8 . A matching catch block.
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Listing 9 . Code following the catch block.
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Listing 10 . Complete program listing for Excep16.
Preview
This module explains Exception Handling in Java. The discussion includes
the following topics:
- What is an exception?
- How do you throw and catch exceptions?
- What do you do with an exception once you have caught it?
- How do you make use of the exception class hierarchy provided by the
Java development environment?
This module will cover many of the details having to do with exception
handling in Java. By the end of the module, you should know that the use ofexception handling is not optional in Java, and you should have a pretty good
idea how to use exception handling in a beneficial way.
Discussion and sample code
Introduction
Stated simply, the exception-handling capability of Java makes it possible
for you to:
- Monitor for exceptional conditions within your program
- Transfer control to special exception-handling code
(which you
design) if an exceptional condition occurs
The basic concept
This is accomplished using the keywords:
try ,
catch ,
throw ,
throws , and
finally . The basic concept is as follows:
- You
try to execute the statements contained within a block of
code.
(A block of code is a group of one or more statements surrounded by
curly brackets.)
- If you detect an exceptional condition within that block, you
throw an exception object of a specific type.
- You
catch and process the exception object using code that you
have designed.
- You optionally execute a block of code, designated by
finally
, which needs to be executed whether or not an exception occurs.
(Code in
the
finally block is normally used to perform some type of cleanup.)
