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created: 04/27/00; revised: 07/06/02, 06/07/03, 07/20/06

CHAPTER 80 — Exceptions and Errors

A program often encounters problems as it executes. It may have trouble reading data, there might be illegal characters in the data, or an array index might go out of bounds. The Java classes Error and Exception enable programmers to deal with such problems. Using them, you can write programs that recover from errors and keep on running. This is important. A word processor program should not crash when the user makes an error!

Chapter Topics:

Input and output is especially error prone. Exception handling is essential for I/O programming, the topic of the next several chapters.

QUESTION 1:

Inspect the following. What went wrong?

C:\cs151\chap80>java  Square 
Enter an integer: rats
Exception in thread "main" java.util.InputMismatchException
        at java.util.Scanner.throwFor(Unknown Source)
        at java.util.Scanner.next(Unknown Source)
        at java.util.Scanner.nextInt(Unknown Source)
        at java.util.Scanner.nextInt(Unknown Source)
        at Square.main(Square.java:12)
        
C:\cs151\chap80>