//  Calculator 3
//  Add some functionality

import javax.swing.* ; 
import java.awt.* ; 
import java.awt.event.* ; 
//
import javax.swing.plaf.metal.* ;

/**
  *  The Calculator panel
  */ 
public class Calculator extends JPanel
                        implements ActionListener {

   private JTextField display ; 

   // first row
   private JButton mc ; 
   private JButton mplus ; 
   private JButton mminus ; 
   private JButton mr ; 
   // second row
   private JButton clear ; 
   private JButton sign ; 
   private JButton divide ;
   private JButton times ; 
   // third row
   private JButton b7 ; 
   private JButton b8 ; 
   private JButton b9 ; 
   private JButton subtract ; 
   // fourth row
   private JButton b4 ; 
   private JButton b5 ; 
   private JButton b6 ; 
   private JButton add ; 
   // fifth row 
   private JButton b1 ; 
   private JButton b2 ; 
   private JButton b3 ; 
   private JButton result ; 
   // sixth row
   private JButton b0 ; 
   private JButton dp ; 


   public Calculator(int fontsize){  
      display = new JTextField("not fully functional") ; 
      display.setHorizontalAlignment(JTextField.RIGHT) ; 
      display.setFont(new Font("monospsced",Font.PLAIN,2*fontsize)) ; 
      display.setForeground(Color.red) ; 

      JPanel keyPad = new JPanel() ; // arrange button/keys here
      // 
      mc = new JButton("MC") ; 
      mplus = new JButton("M+") ; 
      mminus = new JButton("M-") ; 
      mr = new JButton("MR") ; 
      //
      clear = new JButton("C") ; 
      char[] sign_change_unicode = {'\u2213'} ; 
      sign = new JButton(new String(sign_change_unicode)) ; 
      char[] divide_unicode = {'\u00F7'} ; 
      //char[] divide_unicode = {'\u2204'} ; 
      divide = new JButton(new String(divide_unicode)) ; 
      times = new JButton("x") ; 
      //
      b7 = new JButton("7") ; 
      b8 = new JButton("8") ; 
      b9 = new JButton("9") ; 
      subtract = new JButton("-") ; 
      //      
      b4 = new JButton("4") ; 
      b5 = new JButton("5") ; 
      b6 = new JButton("6") ; 
      add = new JButton("+") ; 
      //
      b1 = new JButton("1") ; 
      b2 = new JButton("2") ; 
      b3 = new JButton("3") ; 
      result = new JButton("=") ; 
      //
      b0 = new JButton("0") ; 
      dp = new JButton(".") ; 

      // Add action listener to buttons and set action commands
      b0.addActionListener(this) ; 
      b0.setActionCommand("0") ; 
      b1.addActionListener(this) ; 
      b1.setActionCommand("1") ; 
      clear.addActionListener(this) ; 
      clear.setActionCommand("clear") ; 
      dp.addActionListener(this) ; 
      dp.setActionCommand("dp") ; 

/*    // another way but a little obscure
      b1.setAction(new AbstractAction("1") { 
         public void actionPerformed(ActionEvent a) { 
            display.setText(display.getText()+"1") ; 
         }
      }) ; 

      // or 
      b1 = new JButton(new AbstractAction("1") { ...}) ;
      //  Ok when not many buttons.  
*/

      // set kepPad font
      Font font = new Font("sansserif",Font.PLAIN,fontsize) ;
      mc.setFont(font) ; 
      mplus.setFont(font) ;  
      mminus.setFont(font) ;  
      mr.setFont(font) ;  
      clear.setFont(font) ;  
      sign.setFont(font) ;  
      divide.setFont(font) ;  
      times.setFont(font) ;  
      b7.setFont(font) ;  
      b8.setFont(font) ;  
      b9.setFont(font) ;  
      subtract.setFont(font) ;  
      b4.setFont(font) ;  
      b5.setFont(font) ;  
      b6.setFont(font) ;  
      add.setFont(font) ;  
      mplus.setFont(font) ;  
      b1.setFont(font) ;  
      b2.setFont(font) ;  
      b3.setFont(font) ;  
      result.setFont(font) ;  
      b0.setFont(font) ;  
      dp.setFont(font) ;  

      keyPad.setLayout(new GridLayout(6,4)) ; 

      keyPad.add(mc) ; 
      keyPad.add(mplus) ; 
      keyPad.add(mminus) ; 
      keyPad.add(mr) ; 

      keyPad.add(clear) ; 
      keyPad.add(sign) ; 
      keyPad.add(divide) ; 
      keyPad.add(times) ; 

      keyPad.add(b7) ; 
      keyPad.add(b8) ; 
      keyPad.add(b9) ; 
      keyPad.add(subtract) ; 

      keyPad.add(b4) ; 
      keyPad.add(b5) ; 
      keyPad.add(b6) ; 
      keyPad.add(add) ; 

      keyPad.add(b1) ; 
      keyPad.add(b2) ; 
      keyPad.add(b3) ; 
      keyPad.add(result) ; 

      keyPad.add(b0) ; 
      keyPad.add(dp) ; 

      this.setLayout(new BorderLayout()) ; 
      this.add("North", display) ;
      this.add("Center", keyPad) ; 

      System.out.println(mc.getFont().getSize()) ; 

   } 

   public void actionPerformed(ActionEvent ae) {
      String s = ae.getActionCommand() ; 
      // specify actions here 
      if (s.equals("0")) display.setText(display.getText()+s) ; 
      else if (s.equals("1")) display.setText(display.getText()+s) ;  
      else if (s.equals("clear")) display.setText("") ; 
      else if (s.equals("dp")) display.setText(display.getText()+".") ; 
   }

   /**
     *  Run the calculator from command line.
     */
   public static void main(String[] args) { 
      String laf = UIManager.getSystemLookAndFeelClassName() ;
      System.out.println(laf) ; 
      try { 
         UIManager.setLookAndFeel(laf); 
         //UIManager.setLookAndFeel(new MetalLookAndFeel()); 
      } catch(Exception x) {}
      JFrame frame = new JFrame("Calculator") ; 
      frame.setSize(275,350) ; 
      frame.setLocation(500,500) ; 
      frame.getContentPane().add(new Calculator(16)) ; 
      frame.setVisible(true) ; 
      frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE) ; 
   }
}