//======================================================================
//      Project:    CS 116, Method example
//      Author:     Tom Kelliher
//      File:       Methods.java
//      Purpose:    The applet demonstrates the use of methods.  A
//                  Greetings class is designed and used.  Two Greetings
//                  objects are created and manipulated.
//======================================================================


import java.applet.*;
import java.awt.*;
import java.awt.event.*;


//======================================================================
//      Class:      Methods
//      Purpose:    Create the Greetings objects and a few widgets
//                  (label, buttons) for manipulating them.
//======================================================================

public class Methods extends Applet implements ActionListener
{
   private Greetings today = new Greetings();
   private Greetings tomorrow = new Greetings();

   // The current selected greeting will be displayed via this label.
   private Label greetingLabel = new Label("No greeting selected yet.");

   // Note that there is no Greeting corresponding to the yesterday
   // button, nor does actionPerformed() have the capability of
   // handling the button.  This demonstrates that actionPerformed()
   // must be written to deal with each of the events that are
   // registered for it.
   private Button useYesterday = new Button("Yesterday");
   private Button useToday = new Button("Today");
   private Button useTomorrow = new Button("Tomorrow");


   //===================================================================
   //   Method:     init
   //   Purpose:    Initialize the applet and its widgets.
   //===================================================================

   public void init()
   {
      // Buttons will go into this panel.
      Panel p = new Panel(new GridLayout(1, 3));

      // Note that we're immediately changing today's greeting.
      today.setGreeting("Hi there!!!");

      // greetingLabel will go over the buttons.
      setLayout(new GridLayout(2, 1));

      // Set-up greetingLabel.
      add(greetingLabel);
      greetingLabel.setFont(new Font("Serif", Font.PLAIN, 20));
      greetingLabel.setForeground(Color.green);
      greetingLabel.setBackground(Color.black);

      // Set-up the buttons.
      p.add(useYesterday);
      p.add(useToday);
      p.add(useTomorrow);
      add(p);

      useYesterday.setBackground(Color.magenta);
      useYesterday.addActionListener(this);

      useToday.setBackground(Color.red);
      useToday.addActionListener(this);

      useTomorrow.setBackground(Color.blue);
      useTomorrow.addActionListener(this);
   }


   //===================================================================
   //   Method:     actionPerformed
   //   Purpose:    Handle button presses from useToday and useTomorrow
   //               buttons.
   //   Input:      e, an actionEvent.
   //===================================================================

   public void actionPerformed(ActionEvent e)
   {
      if (e.getActionCommand() == "Today")
         greetingLabel.setText(today.getGreeting());
      else if (e.getActionCommand() == "Tomorrow")
         greetingLabel.setText(tomorrow.getGreeting());
      else   // We got an unexpected event.
         greetingLabel.setText("Huh???");
   }
}


//======================================================================
//      Class:      Greetings
//      Purpose:    This class holds a greeting in a string.  The
//                  default greeting is "Hello."  Two methods are
//                  provided: getGreeting() and setGreeting() (see
//                  below for descriptions).
//======================================================================

class Greetings
{
   private String greeting;


   //===================================================================
   //   Method:     Greetings constructor
   //   Purpose:    Initialize the greeting to the default.
   //===================================================================

   public Greetings()
   {
      greeting = new String("Hello.");
   }


   //===================================================================
   //   Method:     getGreeting
   //   Purpose:    Return the greeting string.
   //   Return:     The greeting string.
   //===================================================================

   public String getGreeting()
   {
      return greeting;
   }


   //===================================================================
   //   Method:     setGreeting
   //   Purpose:    Set the greeting string to newGreeting.
   //   Input:      newGreeting, a string.
   //===================================================================

   public void setGreeting(String newGreeting)
   {
      greeting = newGreeting;

      // This demonstrates that the return statement can be used
      // anywhere, with or without a return value.  This use is
      // redundant, since we're at the end of a void method.  One will
      // usually only see the return statement when it's necessary to
      // return from the middle of a method and/or some sort of a value
      // is being returned.
      return;
   }
}