13.2 IllegalComponentStateException

IllegalComponentStateException is a subclass of IllegalStateException; both are new to Java 1.1. This exception is used when you try to do something with a Component that is not yet appropriate. With the standard AWT components, this can happen only in three instances:

• If you call setCaretPosition() to set the cursor position of a text component before the component's peer exists.

• If you call getLocale() to get the locale of a component that does not have one and is not in a container that has one.

• If you call getLocationOnScreen() for a component that is not showing.

In these cases, the operation isn't fundamentally illegal; you are just trying to perform it before the component is ready. When you create your own components, you should consider using this exception for similar cases.

Since IllegalComponentStateException is a subclass of Run-TimeException, you do not have to enclose method calls that might throw this exception within try/catch blocks. However, catching this exception isn't a bad idea, since it should be fairly easy to correct the problem and retry the operation.

import java.awt.TextField;
public class illegal {
    public static void main (String[] args) {
        new TextField().setCaretPosition (24);
        System.out.println ("Never gets here");
    }
}