converter.java

一些简单的java网络编程实例,对初学者有点用处

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

class Unit 
{
    String description;
    double multiplier;

    Unit(String description, double multiplier) 
    {
        super();
        this.description = description;
        this.multiplier = multiplier;
    }
}

class CPanel extends Panel implements ActionListener,
		                 AdjustmentListener,
		                 ItemListener
{
    TextField TEnter;
    Choice Cchoose;
    
    int max = 10000;
   
    Converter handle;
    Unit[] units;

    CPanel(Converter myController, String myTitle, Unit[] myUnits) 
    {
        GridBagConstraints c = new GridBagConstraints();
        GridBagLayout gridbag = new GridBagLayout();
        setLayout(gridbag);

        handle = myController;
        units = myUnits;

        c.fill = GridBagConstraints.HORIZONTAL;

        Label label = new Label(myTitle, Label.CENTER); 
        c.gridwidth = GridBagConstraints.REMAINDER;
        gridbag.setConstraints(label, c);
        add(label);
        
        TEnter = new TextField("0", 10); 
        c.weightx = 1.0;
        c.gridwidth = 1;
        gridbag.setConstraints(TEnter, c);
        add(TEnter);
	TEnter.addActionListener(this);

        Cchoose = new Choice(); 
        for (int i = 0; i < units.length; i++) 
        {
            Cchoose.add(units[i].description);
        }
        c.weightx = 0.0;
        c.gridwidth = GridBagConstraints.REMAINDER; 
        gridbag.setConstraints(Cchoose, c);
        add(Cchoose);
	Cchoose.addItemListener(this);
    
	c.gridwidth = 1;
       
    }

    double getMultiplier() 
    {
        int i = Cchoose.getSelectedIndex();
        return units[i].multiplier;
    }


    public void paint(Graphics g) 
    {
        Dimension d = getSize();
        g.drawRect(0,0, d.width - 1, d.height - 1);
    }
        

    public Insets getInsets() 
    {
        return new Insets(5,5,5,8);
    }


    double getValue() 
    {
        double f;
        try 
        {
            f = (double)Double.valueOf(TEnter.getText()).doubleValue(); 
        } 
        catch (java.lang.NumberFormatException e) 
        {
            f = 0.0;
        }
        return f;
    }

    public void actionPerformed(ActionEvent e) 
    {
        setSliderValue(getValue());
        handle.Exchange(this);
    }

    public void itemStateChanged(ItemEvent e) 
    {
        handle.Exchange(this);
    }

    public void adjustmentValueChanged(AdjustmentEvent e) 
    {
        TEnter.setText(String.valueOf(e.getValue()));
        handle.Exchange(this);
    }

    void setValue(double f) 
    {
        setSliderValue(f);
        TEnter.setText(String.valueOf((float)f));
    }

    void setSliderValue(double f) 
    {
        int sliderValue = (int)f;

        if (sliderValue > max)
               sliderValue = max;
        if (sliderValue < 0)
            sliderValue = 0;
    }
}
public class Converter extends Applet 
{
    private CPanel MPanel, UPanel;
    private Unit[] ChoiceM = new Unit[3];
    private Unit[] ChoiceU = new Unit[4];


    public void init() 
    {

        setLayout(new GridLayout(2,0,5,5));

        ChoiceM[0] = new Unit("公分", 0.01);
        ChoiceM[1] = new Unit("公尺", 1.0);
        ChoiceM[2] = new Unit("公里", 1000.0);
        MPanel = new CPanel(this, "公制",ChoiceM);

        MPanel.setBackground(Color.white);
        
        ChoiceU[0] = new Unit("英吋", 0.0254);
        ChoiceU[1] = new Unit("英呎", 0.305);
        ChoiceU[2] = new Unit("码", 0.914);
        ChoiceU[3] = new Unit("英哩", 1613.0);
        
        UPanel = new CPanel(this, "英制", ChoiceU);
        UPanel.setBackground(Color.white);

        add(MPanel);
        add(UPanel);
    }

    void Exchange(CPanel from) {
        CPanel to;

        if (from == MPanel)
            to = UPanel;
        else
            to = MPanel;

        double multiplier = from.getMultiplier() / to.getMultiplier();
        to.setValue(multiplier * from.getValue());
    }

    public void paint(Graphics g) 
    {
        Dimension d = getSize();
        g.drawRect(0,0, d.width - 1, d.height - 1);
    }
        

    public Insets getInsets() 
    {
        return new Insets(5,5,5,5);
    }
    
}