import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.util.StringTokenizer;

public class TextTest
{  

   public static JTextArea inputArea;       // Text area for input
   public static JTextField resultField;    // Text area for output
   public static JButton calcButton;        // Button to trigger calculation

   public static void main(String[] args)
   {  

      JFrame f = new JFrame("TextTest");


      /* ++++++++++++++++++++++++++++++++++++++++++
         1. Construct the components
         ++++++++++++++++++++++++++++++++++++++++++ */

      // ===========================
      // 1. a text area for input
      // ===========================
      inputArea = new JTextArea();        // Default is editable...
   
      // ===========================
      // 2. a text area for output
      // ===========================
      resultField = new JTextField(20);
      resultField.setEditable(false);     // No editing allowed here....
      
      // ================================
      // 3. a button to start the show
      // ================================
      calcButton = new JButton("Calculate");
      
      /* ------------------------------------
	 add components to content pane
         ------------------------------------ */

      /* ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
	 2. Place the components in JFrame
         ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ */
      
      // ======================================================
      // Pick Layout manager first !!!
      // ======================================================
      f.getContentPane().setLayout( new BorderLayout() );

      // ======================================================
      // Place JTextArea at center
      // ======================================================
      f.getContentPane().add(inputArea, "Center");
      
      // ======================================================
      // This is for extra sexy effect:
      //               +----------+-------------------------+
      //               | Average: | (output text field)     |
      //               +----------+-------------------------+
      // ======================================================
      JPanel resultPanel = new JPanel();	// JPanel for sexy effect
      resultPanel.add(new JLabel("Average: ")); // Add label first
      resultPanel.add(resultField);		// Then add output text area

      // ======================================================
      // Another JPanel for extra sexy effect:
      //               +-----------------+
      //               |    Calculate    |
      //               +-----------------+
      // ======================================================

      JPanel buttonPanel = new JPanel();	// Make a panel
      buttonPanel.add(calcButton);		// Add Calculate button

      // ======================================================
      // A third JPanel to make it ultra sexy....
      // We stack up these previous two panels in this JPanel
      // like this:
      //              +--------------------------------------+
      //              |+----------+-------------------------+|
      //              || Average: | .....(output text area) ||
      //              |+----------+-------------------------+|
      //              |         +-----------------+          |
      //              |         |    Calculate    |          |
      //              |         +-----------------+          |
      //              +--------------------------------------+
      // ======================================================

      JPanel southPanel = new JPanel();		   // Make a panel
      southPanel.setLayout(new GridLayout(2, 1));  // We need a Grid layout...
      southPanel.add(resultPanel);		   // Add first panel
      southPanel.add(buttonPanel);		   // Stack second panel

      // ========================================================
      // Finally, put the stacked panels at "South" of JFrame
      // ========================================================
      f.getContentPane().add(southPanel, "South");

      // ++++++++++++++++++++++++++++++++++++++++++++++++++++++
      // OK, make-up session is over, only thing left is
      // to make the GUI alive....
      // ++++++++++++++++++++++++++++++++++++++++++++++++++++++

      /* ++++++++++++++++++++++++++++++++++++++++++
	 3. Register Listener for (some) components
         ++++++++++++++++++++++++++++++++++++++++++ */
      calcButton.addActionListener(new ButtonListener()); // Press to calculate!

      f.setSize(500, 500);                  // Set frame size
      f.setVisible(true);
   }
   
   
   /* =============================================================
      Listener class for the Calculate button
      ============================================================= */
   public static class ButtonListener implements ActionListener
   {  
      public void actionPerformed(ActionEvent event)
      {  
	 String input;
         double sum;
	 int i, N;

	 // get user input from text area
	 input = inputArea.getText();  // <------ how to get text typed in
					   //         a JTextArea object

	 // Tokenize the string
	 StringTokenizer tokenizer = new StringTokenizer(input);
         
	 N = tokenizer.countTokens();
	 sum = 0;
	 for ( i = 0; i < N; i++ )
	    sum += Double.parseDouble(tokenizer.nextToken());

         // display in result field
         resultField.setText("" + sum/N);
      }
   }   
}