calc.java

java计算器计算功能强大

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

public class Calc extends Applet implements ActionListener
{
	TextField expText, resText;
	Parser p;

	public void init()
	{
		Label heading=new Label("Expression Calculator",Label.CENTER);
		Label explab=new Label("Expression",Label.CENTER);
		Label reslab=new Label("Result     ",Label.CENTER);
		expText=new TextField(24);
		resText=new TextField(24);

		resText.setEditable(false);

		add(heading);
		add(explab);
		add(expText);
		add(reslab);
		add(resText);

		expText.addActionListener(this);
		p=new Parser();

	}

	public void actionPerformed(ActionEvent e)
	{
		repaint();
	}

	public void paint(Graphics g)
	{
		double result=0.0;
		String expstr=expText.getText();

		try
		{
			if (expstr.length()!=0)
			{
				result=p.evaluate(expstr);}
				expText.setText(" ");
				resText.setText(Double.toString(result));
				showStatus("");
			
		}
		catch (ParserException e)
		{
			showStatus(e.toString());
			resText.setText(" ");

		}
	}


}