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

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

/**
   A frame with a calculator panel.
*/
class CalculatorFrame extends JFrame
{
   public CalculatorFrame()
   {
      super("Calculator");
                                                                
      Container contentPane = getContentPane();
      setSize(400,300);
	  setLocation(0,0);
   
      CalculatorPanel panel = new CalculatorPanel();
      contentPane.add(panel);
	
   }
}

class CalculatorPanel extends JPanel
{  
   public CalculatorPanel()
   {  
      setLayout(new BorderLayout());//設定布局
      
	  init();	
      
	  //顯示區域
      display = new JTextField("0.");
	  display.setHorizontalAlignment(JTextField.RIGHT );
      
	  display.setBackground(Color.white);
      display.setEditable(false);
      add(display,BorderLayout.CENTER);
	                   
     //鍵盤區域
      ActionListener insert = new InsertAction();
      ActionListener command = new CommandAction();

      panel = new JPanel();
      panel.setLayout(new GridLayout(5,6,6,15));

      dispM=new JTextField("");
	  dispM.setEditable(false);
      dispM.setBackground(Color.white.brighter());
	  panel.add(dispM);
	
	  addButton("C", command);
      addButton("CE",command);
      addButton("退格",command);
	  addButton("=", command);
      addButton("   ",command);
      
      addButton("MC",command);
      addButton("7", insert);
      addButton("8", insert);
      addButton("9", insert);
      addButton("/", command);
      addButton("sqrt",command);

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

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

      addButton("M+", command);
      addButton("0", insert);
      addButton("+/-", command);
      addButton(".", insert);
      addButton("+",command);
	  addButton("ran", command);
      add(panel,BorderLayout.SOUTH);
   }

   private void init()
   {
   	  result = 0;
      lastCommand = "=";
      start = true;
     tag=true;
   }

 
   private void addButton(String label, ActionListener listener)
   {  
      JButton button = new JButton(label);
      button.addActionListener(listener);
	  button.setBackground(Color.white.brighter());
      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);
      }
   }

   //監聽按鈕項的按下動作
   private class CommandAction implements ActionListener
   {
      public void actionPerformed(ActionEvent evt)
      {  
         String command = evt.getActionCommand();
		 if (command.equals("C"))
		 	{
		 		init();//之前的數被清空
	            display.setText("0");
	        }		  
		else if(command.equals("CE"))
		    {
			display.setText(" ");//之前的數還在result中
			start=true;
		    }
		else if(command.equals("退格"))
		  {
			String tem=display.getText();
			String t=tem.substring(0,tem.length()-1);
			display.setText(t);
		  }
		else if(command.equals("ran"))
		  {
			
			display.setText(""+Math.random());
		  }
		else if(command.equals("MS"))
		  {
			mem=Double.parseDouble(display.getText());
			dispM.setText("M");
			start=true;
		  }
		else if(command.equals("MR"))
		  {
			display.setText(""+mem);
			
		  }
		else if(command.equals("MC"))
		  {
			dispM.setText("");
			mem=0;
		  }
		else if(command.equals("M+"))
		  {
			dispM.setText("M");
			double p=Double.parseDouble(display.getText());
			mem+=p;
			display.setText(""+mem);
			start=true;
		  }
        else if (command.equals("+/-")) 
            { 
			   String tmp=display.getText();
			   char sign=tmp.charAt(0);
			   if (sign=='-')tag=false;
			   else tag=true;
               if(tag)
               {    
               		display.setText("-"+display.getText()); 
               		tag=false;
               	}
               	else
         		{
         			String t=tmp.substring(1,tmp.length());
         			display.setText(t);
         			tag=true;
         		}
            }
         else
         {  
            calculate(Double.parseDouble(display.getText()));//將運算符前的字符串轉化成數字
            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 =0.01*x;
	 
	  else if (lastCommand.equals("1/x")) result=1/x;
	  else if (lastCommand.equals("sqrt")) result=Math.sqrt(x);
	 
      else if (lastCommand.equals("=")) result = x;
	  
      display.setText("" + result);  	 
   }
   
   private JTextField display;
   private JTextField dispM;
   private JPanel panel;
   private double result;
   private boolean tag;
   private String lastCommand;
   private boolean start;
   private double mem;
   private double copy;
}

/*使用存儲的數
要存儲顯示的數據，請單擊“MS”。 
要重新調用存儲的數據，請單擊“MR”。 
要清除內存，請單擊“MC”。 
把所顯示的數字與內存中的數字相加，請單擊“M+”。要查看新數據，請單擊“MR”。 
 注意

存儲數據時，存儲選項上方的框中會顯示出“M”。存入其他數據時，存儲器中的數據將被替換。 
*/