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CIS 270—Application Development II. Chapter 13—Exception Handling. 13.1-3 Introduction & Overview. An exception is an indication of a problem during program ___________. A program that ________ exceptions keeps running.
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CIS 270—Application Development II Chapter 13—Exception Handling
13.1-3 Introduction & Overview • An exception is an indication of a problem during program ___________. • A program that ________ exceptions keeps running. • Interjecting program logic with error-handling logic in a program creates maintenance problems. • If an exception occurs and is not handled, it is _________. • The error message produced by Java is called a stack _______, which consists of the exception name and the method-call stack. • You can trace an exception starting at the top.
13.4 Handling Exceptions 1 • If you don’t want a method to handle an exception, you should code a ________ clause at the end of the method declaration. • A throws clause can list one or more exceptions. • To handle an exception, you should enclose the code that could throw an exception in a _____ block. • Code that handles the exception is placed immediately after the try block in a _______ block. • A try block must be followed by at least one catch block or a finally block. • A catch block can handle only one kind of exception.
13.4 Handling Exceptions 2 • When an exception occurs in a try block, control is passed to the appropriate catch block, after which control resumes after the _______ catch block. • This is called the ___________ model because the try block is terminated (instead of resuming in the try block after the exception is handled). • A try ___________ is the combination of the try block and all catch and finally blocks. • If an exception occurs, the method or try block terminates and local variables go out of _______ and are destroyed.
13.6 Java Exception Hierarchy 1 • The Throwable class has two subclasses: Exception and Error • It is usually not possible for a program to recover from Errors (such as out of __________). • All Java exception classes inherit from Exception. • The Exception class has two subclasses: RuntimeException and IOException. • ___________ exceptions are only those that inherit from RuntimeException, such as division by 0. • All others are checked exceptions, which MUST be thrown or handled (or program will not _________).
13.6 Java Exception Hierarchy 2 • The Java compiler checks your code for the possibility of checked exceptions and will force you to catch or throw (________) such exceptions. • __________ exceptions (like division by 0) can be prevented by proper coding and do not need to be listed in a throws clause. • catch blocks must be ordered with subclass exceptions coming _______ superclass exceptions (or else you will lose specific exception information).
13.7 finally Block • If data files are not closed by a program, they may not be available to other programs. • This is an example of a __________ leak. • A finally block is placed after the last catch block. • The finally block will always execute unless a try block calls ____________. • A finally block usually contains resource-___________ code. • The output stream System.err allows the programmer to deal with error messages separately.
