calpanel.java

JAVA计算器+Apllet应用+要二十个字

import java.awt.BorderLayout;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;



public class CalPanel extends JPanel
{
	private JLabel display;
	private JPanel panel;
	private double result;
	private String lastCommand;
	private boolean start;

	private void addButton(String label,ActionListener listener){
		JButton button=new JButton(label);
		button.addActionListener(listener);
		panel.add(button);
	}
	
	public CalPanel(){
		setLayout(new BorderLayout());
		result=0;
		lastCommand="=";
		start=true;
		display=new JLabel("0");
		add(display,BorderLayout.NORTH);
		panel=new JPanel();
		panel.setLayout(new GridLayout(4,3));
		ActionListener insert=new InsertAction();
		ActionListener command=new CommandAction(); 
		addButton("7",insert);
		addButton("8",insert);
		addButton("9",insert);
		
		addButton("4",insert);
		addButton("5",insert);
		addButton("6",insert);
		
		addButton("1",insert);
		addButton("2",insert);
		addButton("3",insert);
		
		addButton("0",insert);
		addButton("=",command);
		addButton("+",command);
		JTextArea textArea = new JTextArea(8, 20);
		JScrollPane scrollPane = new JScrollPane(textArea);
		add(panel,BorderLayout.CENTER);
		add(scrollPane,BorderLayout.EAST);
		textArea.setText("庞玉彤 ，文计071-2，200790513221");
	}
	private class InsertAction implements ActionListener{
		public void actionPerformed(ActionEvent event){
			String input=event.getActionCommand();
			if(start){
				display.setText("");
				start=false;
			}
			display.setText(display.getText()+input);
			
		}
	}
	private class CommandAction implements ActionListener{
		String 	lastcommand="+";
		public void actionPerformed(ActionEvent event2)
		{
			String command=event2.getActionCommand();

				if(command=="+"){
					result=Double.parseDouble(display.getText());
					display.setText(display.getText());
					start=true;
					lastcommand=command;
				}
				
				if(command=="="){
					if(lastcommand=="+"){
						result+=Double.parseDouble(display.getText());		
						lastcommand="=";
					}else{
						display.setText(""+result);
					}

					display.setText(""+result);
					start=true;
				}
				

		}
	}
}