    01: import java.awt.event.*;
    02: import javax.swing.*;
    03:
    04: /**
    05:    This action places a greeting into a text field
    06:    and afterwards disables itself and enables its
    07:    opposite action.
    08: */
    09: public class GreetingAction extends AbstractAction
    10: {
    11:    /**
    12:       Constructs a greeting action.
    13:       @param greeting the string to add to the text area
    14:       @param textArea the text area to which to add the greeting
    15:    */
    16:    public GreetingAction(String greeting, JTextArea textArea)
    17:    {
    18:       this.greeting = greeting;
    19:       this.textArea = textArea;
    20:    }
    21:
    22:    /**
    23:       Sets the opposite action.
    24:       @param the action to be enabled after this action was
    25:       carried out
    26:    */
    27:    public void setOpposite(Action action)
    28:    {
    29:       oppositeAction = action;
    30:    }
    31:
    32:    public void actionPerformed(ActionEvent event)
    33:    {
    34:       textArea.append(greeting);
    35:       textArea.append("\n");
    36:       if (oppositeAction != null)
    37:       {
    38:          setEnabled(false);
    39:          oppositeAction.setEnabled(true);
    40:       }
    41:    }
    42:
    43:    private String greeting;
    44:    private JTextArea textArea;
    45:    private Action oppositeAction;
    46: }