Exception-Handling Overview

Programs frequently test conditions to determine how program execution should proceed. Consider the following pseudocode:


       Perform a task

       If the preceding task did not execute correctly
             Perform error processing

       Perform next task

       If the preceding task did not execute correctly
             Perform error processing

       ...

In this pseudocode, we begin by performing a task; then we test whether that task executed correctly. If not, we perform error processing. Otherwise, we continue with the next task. Although this form of error handling works, intermixing program logic with error-handling logic can make programs difficult to read, modify, maintain and debugespecially in large applications.

Performance Tip 13.1

If the potential problems occur infrequently, intermixing program and error-handling logic can degrade a program's performance, because the program must perform (potentially frequent) tests to determine whether the task executed correctly and the next task can be performed.

Exception handling enables programmers to remove error-handling code from the "main line" of the program's execution, improving program clarity and enhancing modifiability. Programmers can decide to handle any exceptions they chooseall exceptions, all exceptions of a certain type or all exceptions of a group of related types (i.e., exception types that are related through an inheritance hierarchy). Such flexibility reduces the likelihood that errors will be overlooked, thus making programs more robust.

With programming languages that do not support exception handling, programmers often delay writing error-processing code or sometimes forget to include it. This results in less robust software products. Java enables programmers to deal with exception handling easily from the inception of a project.

Introduction to Computers, the Internet and the World Wide Web

Introduction to Java Applications

Introduction to Classes and Objects

Control Statements: Part I

Control Statements: Part 2

Methods: A Deeper Look

Arrays

Classes and Objects: A Deeper Look

Object-Oriented Programming: Inheritance

Object-Oriented Programming: Polymorphism

GUI Components: Part 1

Graphics and Java 2D™

Exception Handling

Files and Streams

Recursion

Searching and Sorting

Data Structures

Generics

Collections

Introduction to Java Applets

Multimedia: Applets and Applications

GUI Components: Part 2

Multithreading

Networking

Accessing Databases with JDBC

Servlets

JavaServer Pages (JSP)

Formatted Output

Strings, Characters and Regular Expressions

Appendix A. Operator Precedence Chart

Appendix B. ASCII Character Set

Appendix C. Keywords and Reserved Words

Appendix D. Primitive Types

Appendix E. (On CD) Number Systems

Appendix F. (On CD) Unicode®

Appendix G. Using the Java API Documentation

Appendix H. (On CD) Creating Documentation with javadoc

Appendix I. (On CD) Bit Manipulation

Appendix J. (On CD) ATM Case Study Code

Appendix K. (On CD) Labeled break and continue Statements

Appendix L. (On CD) UML 2: Additional Diagram Types

Appendix M. (On CD) Design Patterns

Appendix N. Using the Debugger

Inside Back Cover

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Java(c) How to Program
Java How to Program (6th Edition) (How to Program (Deitel))
ISBN: 0131483986
EAN: 2147483647
Year: 2003
Pages: 615
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