calculator2.java

国外的一些较好的APPLET收集(含原码)!

import java.awt.*;
import java.applet.*;
import java.io.*;
import corejava.*;

public class Calculator2 extends Applet
{	public void init()
	{	setLayout(new BorderLayout());

		Panel P = new Panel ();
        P.setLayout (new GridLayout(2,1));
	    title=getParameter("title");
        Title = new Label(title);
	    P.add(Title);

		display = new TextField("0",35);
		display.setEditable(false);
		P.add(display);
		add("North", P);

		
		Panel p = new Panel();
		p.setLayout (new GridLayout(5,4));
		p.add(new Button("7"));
		p.add(new Button("8"));
		p.add(new Button("9"));
		p.add(new Button("/"));
		p.add(new Button("4"));
		p.add(new Button("5"));
		p.add(new Button("6"));
		p.add(new Button("*"));
		p.add(new Button("1"));
		p.add(new Button("2"));
		p.add(new Button("3"));
		p.add(new Button("-"));
		p.add(new Button("0"));
		p.add(new Button("."));
		p.add(new Button("="));
		p.add(new Button("+"));
		p.add(new Button("Clear"));
		add("Center", p);
}


	public boolean action(Event evt, Object arg)
	{	if	(arg instanceof String)
		{	String s = (String) arg;
			char ch = s.charAt(0);
			 if (ch == 'C') {resetCalculator(); start=true; return true;}
			if ('0' <= ch && ch <= '9' || ch == '.')
			{	if (start) display.setText(s);
				else display.setText(display.getText() + s);
				start = false;
							}
			else
				
			{	if (start) 
				{	if (s.equals("-"))
					{ display.setText(s); start = false; }
					else op = s;
				}
				else
				{	calculate(Format.atof(display.getText()));
					op = s;
					start = true;
				}
			}
		}
		else return super.action(evt, arg);
		return true;
	}

	public void resetCalculator()
			{	display.setText ("0");
				arg=0;
				start=true;
			}

	public void calculate(double n)
	{	if (op == "+") arg += n;
		else if (op == "-") arg -= n;
		else if (op == "*") arg *= n;
		else if (op == "/") arg /= n;
		else if (op == "=") arg = n;
		display.setText("" + arg);
	}
	private TextField display;
	private Label Title;
	private String title;

	private double arg = 0;
	private String op = "=";
	private boolean start = true;

}