[Chapter 13] 13.3 AWTError

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| Chapter 13 AWT Exceptions and Errors |

## 13.3 AWTError

`AWTError` is a subclass of `Error` that is used when a serious run-time error has occurred within AWT. For example, an `AWTError` is thrown if the default `Toolkit` cannot be initialized or if you try to create a `FileDialog` within Netscape Navigator (since that program does not permit local file system access). When an `AWTError` is thrown and not caught, the virtual machine stops your program. You may throw this `Error` to indicate a serious run-time problem in any subclass of the AWT classes. Using `AWTError` is slightly preferable to creating your own `Error` because you don't have to provide another class file. Since it is part of Java, `AWTError` is guaranteed to exist on the run-time platform.

Methods are not required to declare that they throw `AWTError`. If you throw an error that is not caught, it will eventually propagate to the top level of the system.

### AWTError Method

Constructor

public AWTError (String message)

  The sole constructor creates an `AWTError` with a detail message of `message`. This message can be retrieved using `getMessage()`, which it inherits from `Error` (and is required by the `Throwable` interface). If you do not want a detailed message, `message` may be `null`.

### Throwing an AWTError

The code in Example 13.1 throws an `AWTError` if it is executed with this command:

    java -Dawt.toolkit=foo throwme

The error occurs because the Java interpreter tries to use the `toolkit foo`, which does not exist (assuming that class `foo` does not exist in your `CLASSPATH`). Therefore, `getDefaultToolkit()` throws an `AWTError`, and the next statement never executes.

#### Example 13.1: The throwme class

    import java.awt.Toolkit;
    public class throwme {
        public static void main (String[] args) {
            System.out.println (Toolkit.getDefaultToolkit());
            System.out.println ("Never Gets Here");
        }
    }

IllegalComponentStateException |  | And Then There Were Applets