/*
 * GUIEventsDemo.java - demonstration of using GUI evemts
 *
 * This program asks the user to enter a number, the outputs its square root
 *
 * Copyright (c) 2000, 2004 - Russell C. Bjork
 *
 */
 
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class GUIEventsDemo extends JApplet implements ActionListener
{
	/** Constructor - create the GUI */
	
    public GUIEventsDemo()
    {
        // We'll use absolute positioning
        getContentPane().setLayout(null);
        
        numberPrompt = new JLabel("Please enter a positive number");
        getContentPane().add(numberPrompt);
        numberPrompt.setBounds(50, 50, 200, 20);
        
        numberInput = new JTextField(20);
        getContentPane().add(numberInput);
        numberInput.setBounds(270, 50, 80, 20);
        
        computeButton = new JButton("Compute square root");
        getContentPane().add(computeButton);
        computeButton.setBounds(100, 150, 200, 20);
        
        result = new JLabel("", SwingConstants.CENTER);
        getContentPane().add(result);
        result.setBounds(50, 250, 300, 20);
        
        // Prepare to handle mouse click on the compute button
        
        computeButton.addActionListener(this);
    }
      
    /** Method invoked when the user clicks the compute button */
    
    public void actionPerformed(ActionEvent e)
    {
        // Get the number the user typed:
        
        String numberTyped = numberInput.getText();
        
        // Convert it to a float - code borrowed from Wu
        
        Double doubleObj = new Double(numberTyped);
        double value = doubleObj.doubleValue();
        
        // Compute its square root and put it in the result label
        
        double sqrt = Math.sqrt(value);
        result.setText("Square root is " + sqrt);
    }
      
    // Instance variables - components of the GUI
    
    private JLabel numberPrompt;
    private JTextField numberInput;
    private JButton computeButton;
    private JLabel result;
}