celsiusconverter.java

初期JAVA学习非常有用的资料。帮助深入了解API。特别是Applet。

//v 1.3
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

// This example demonstrates the use of JButton, JTextField
// and JLabel.
public class CelsiusConverter implements ActionListener {
    JFrame converterFrame;
    JPanel converterPanel;
    JTextField tempCelsius;
    JLabel celsiusLabel, fahrenheitLabel;
    JButton convertTemp;

    // Constructor
    public CelsiusConverter() {
	// Create the frame and container.
	converterFrame = new JFrame("Convert Celsius to Fahrenheit");
	converterFrame.setSize(40, 40);
	converterPanel = new JPanel();
	converterPanel.setLayout(new GridLayout(2, 2));
	
	// Add the widgets.
	addWidgets();

	// Add the panel to the frame.
	converterFrame.getContentPane().add(converterPanel, BorderLayout.CENTER);

	// Exit when the window is closed.
        converterFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

	// Show the converter.
	converterFrame.pack();
	converterFrame.setVisible(true);
    }

    // Create and add the widgets for converter.
    private void addWidgets() {
	// Create widgets.
	tempCelsius = new JTextField(2);
	celsiusLabel = new JLabel("Celsius", SwingConstants.LEFT);
	convertTemp = new JButton("Convert...");
	fahrenheitLabel = new JLabel("Fahrenheit", SwingConstants.LEFT);

	// Listen to events from Convert button.
	convertTemp.addActionListener(this);

	// Add widgets to container.
	converterPanel.add(tempCelsius);
	converterPanel.add(celsiusLabel);
	converterPanel.add(convertTemp);
	converterPanel.add(fahrenheitLabel);
	
        celsiusLabel.setBorder(BorderFactory.createEmptyBorder(5,5,5,5));
	fahrenheitLabel.setBorder(BorderFactory.createEmptyBorder(5,5,5,5));
	
    }

    // Implementation of ActionListener interface.
    public void actionPerformed(ActionEvent event) {
      	// Parse degrees Celsius as a double and convert to Fahrenheit.
        int tempFahr = (int)((Double.parseDouble(tempCelsius.getText()))
                             * 1.8 + 32);
	fahrenheitLabel.setText(tempFahr + " Fahrenheit");
    }

    // main method
    public static void main(String[] args) {
	// Set the look and feel.
	try {
	    UIManager.setLookAndFeel(
		UIManager.getCrossPlatformLookAndFeelClassName());
	} catch(Exception e) {}

	CelsiusConverter converter = new CelsiusConverter();
    }
}