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Help is available for each task.



    Task 1

    To handle selections in the Choice object, design a class that implements ItemListener. When an item is selected, the applet should look up the name in the phonebook hashtable and display the number found in the entryField text field.


    Create a class that implements the ItemListener interface and define its itemStateChanged() method.
    To get the string to look up, use the getItem() method of the ItemEvent parameter to the method.
    Use the Hashtable.get() method to look for the item in the phonebook.
    Use the TextField.setText() method to change the entryField contents.
    The Toolkit.beep() method plays a beep. Use the Component.getToolkit() method to get a Component to use.

    Task 2

    Register the ItemListener with the Choice object.


    Call the Choice.addItemListener() method with the instance of the class that implements the ItemListener interface as the argument.

    Task 3

    To handle text entry and the look-up operation for the telephone number, design a class that implements ActionListener. The phone number from the text field should be looked up in the reversePhonebook hashtable and the appropriate name displayed in the bookChoice pull-down list.


    Create a class that implements the ActionListener interface and define its actionPerformed() method.
    To get the string to look up, use the getText() method of TextField.
    Use the Hashtable.get() method to look for the item in the reversePhonebook.
    Use the Choice.select() method to move to the appropriate item in the Choice instance.
    Use the Toolkit.beep() method to play a beep if no match is found.

    Task 4

    Instantiate the class (once) that implements ActionListener and register it with the TextField and Button instances.


    Call the addActionListener() method with the instance that implements the interface as the argument.
    Make sure the same listener is added to both classes. You do not need to create two instances of the class that implements the interface.

    Task 5

    To restrict input in the TextField, design a class that implements KeyListener or subclasses KeyAdapter. Use this class to reject textfield input that is not a digit or '-'.


    Because only one method in the KeyListener interface is needed, namely, keyTyped(), it's more convenient to subclass KeyAdapter, which supplies the other methods in the interface.
    Use the Character.isDigit() method to check for numerical input.
    To reject inappropriate input, call the consume() method of the event.

    Task 6

    To ensure errors can be deleted and retain normal functionality for the Enter and Tab keys, let the Backspace, Delete, Tab, and Enter keys be valid characters for the keyTyped() method also.



    The KeyEvent class has constants for the four characters to check.

    Task 7

    Register the object that implements KeyListener with the TextField instance.


    Call the addKeyListener() method with the class that implements the interface as the argument.

    Task 8

    Use the Phone.html file in the solution to test it.


    Shift-Click on Phone.html to save.

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[ This page was updated: 15-Jul-2000 ]
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