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Chapter 13 |  |
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Chapter 13 | |
Contents:
AWTException
IllegalComponentStateException
AWTError
This chapter describes AWTException, IllegalComponentStateException, and AWTError. AWTException is a subclass of Exception. It is not used by any of the public classes in java.awt; you may, however, find it convenient to throw AWTException within your own code. IllegalComponentStateException is another Exception subclass, which is new to Java 1.1. This exception is used when you try to do something with a Component that is not yet appropriate. AWTError is a subclass of Error that is thrown when a serious problem occurs in AWT--for example, the environment is unable to get the platform's Toolkit.
AWTException is a generic exception that can be thrown when an exceptional condition has occurred within AWT. None of the AWT classes throw this. If you subclass any of the AWT classes, you can throw an AWTException to indicate a problem. Using AWTException is slightly preferable to creating your own Exception subclass because you do not have to generate another class file. Since it is a part of Java, AWTException is guaranteed to exist on the run-time platform.
If you throw an instance of AWTException, like any other Exception, it must be caught in a catch clause or declared in the throws clause of the method.
The sole constructor creates an AWTException with a detailed message of message. This message can be retrieved using getMessage(), which it inherits from Exception (and which is required by the Throwable interface). If you do not want a detailed message, message may be null.
An AWTException is used the same way as any other Throwable object. Here's an example:
if (someProblem) {
throw new AWTException ("Problem Encountered While Initializing");
}
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IllegalComponentStateException |
