[Chapter 13] AWT Exceptions and Errors

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| Chapter 13 |

# 13. AWT Exceptions and Errors

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`.

## 13.1 AWTException

`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.

### AWTException Method

Constructor

public AWTException (String message)

  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`.

### Throwing an AWTException

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");
    }

ImageFilter |  | IllegalComponentStateException