calculator.java

计算器小程序

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;



public class Calculator
{
	public static void main(String[] args)
	{
		CalculatorFrame frame = new CalculatorFrame();
		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		frame.setVisible(true);
		}
	}

class CalculatorFrame extends JFrame
{ public CalculatorFrame()
   {setTitle("C.");
	CalculatorPanel panel = new CalculatorPanel();
	add(panel);
	pack();
    }
 }

 class CalculatorPanel extends JPanel
 {
	 public CalculatorPanel()
	 {
		 setLayout(new BorderLayout());

		 result=0;
		 lastCommand="=";
		 start = true;

		 display = new JButton("0");
		 display.setEnabled(false);
		 add(display,BorderLayout.NORTH);

		 ActionListener insert = new InsertAction();
		 ActionListener command= new CommandAction();

         /*设置网格布局*/
		 panel = new JPanel();
		 panel.setLayout(new GridLayout(4,4));


		 addButton("7",insert);
		 addButton("8",insert);
		 addButton("9",insert);
		 addButton("/",command);

		 addButton("4",insert);
		 addButton("5",insert);
		 addButton("6",insert);
		 addButton("*",command);


		 addButton("1",insert);
		 addButton("2",insert);
		 addButton("3",insert);
		 addButton("-",command);

		 addButton("0",insert);
		 addButton(".",insert);
		 addButton("=",command);
		 addButton("+",command);

		 add(panel,BorderLayout.CENTER);

		 }


		 private void addButton(String label,ActionListener listener)
		 {
			 JButton button = new JButton(label);
			 button.addActionListener(listener);
			 panel.add(button);

			 }


		 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
	 {
		 public void actionPerformed(ActionEvent event){

			 String command = event.getActionCommand();


			 if(start)
			 {
				 if(command.equals("-"))
				 {
					 display.setText(command);
					 start = false;
				 }
				 else
				    lastCommand = command;
				 }
				 else
				 {calculate(Double.parseDouble(display.getText()));
				  lastCommand = command;
				  start = true;
					 }

			 }
	 }

		 public void calculate(double x)
		 {
			 if(lastCommand.equals("+")) result +=x;
			 else if (lastCommand.equals("-")) result -=x;
			 else if (lastCommand.equals("*")) result *=x;
			 else if (lastCommand.equals("/")) result /=x;
			 else if (lastCommand.equals("=")) result =x;
			 display.setText(""+result);


			 }

			 private JButton display;
			 private JPanel panel;
			 private double result;
			 private String lastCommand;
			 private boolean start;






			 }