+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
import java.awt.*;

class kalk1  // save as kalk1.java
  {
    public static void main (String [] args)
      {
        NumberCruncher1 C = new NumberCruncher1("yummypoos");
      }
  }
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// General import statements:
import java.awt.*;
import java.awt.event.*;
import java.io.*;  

///////////////////////////////////////////////////////////////////////
//                   The NumberCruncher2 class definition            //
///////////////////////////////////////////////////////////////////////
public class NumberCruncher1 extends Frame 
                             implements ActionListener, WindowListener
  {
    private TextField display = new TextField(10);
    private Button [] nobs = new Button[15];

    static String [] keys = {" 0 "," 1 "," 2 "," 3 "," 4 ",
                             " 5 "," 6 "," 7 "," 8 "," 9 ",
                             " + "," - "," = "," * "," / "};
    private StringBuffer regA = new StringBuffer();
    private StringBuffer regB = new StringBuffer();
    private char operator;
    private boolean firstNoIn = false;

    public NumberCruncher1( String s )
      {
        super(s);
        setBackground(Color.yellow);
        addWindowListener(this);
        setLayout(new FlowLayout(FlowLayout.CENTER));
        add(display);
        Panel pad = new Panel();
        pad.setLayout(new GridLayout(5,3));
        for (int i=0; i<keys.length; i++)
          { nobs[i] = new Button(keys[i]);
            nobs[i].addActionListener(this);
            pad.add(nobs[i]);
          }
        add(pad);
        setSize(150,299);
        show();
      } // --------------- end of constructor

    // ---------- implementing WindowListener methods -----------
    public void windowClosed(WindowEvent evt){}
    public void windowDeiconified(WindowEvent evt){}
    public void windowIconified(WindowEvent evt){}
    public void windowActivated(WindowEvent evt){}
    public void windowDeactivated(WindowEvent evt){}
    public void windowOpened(WindowEvent evt){}
    public void windowClosing(WindowEvent evt){ System.exit(0); }

    public void actionPerformed(ActionEvent evt)
      {
        final int posEq = 12;
        Object source = evt.getActionCommand();
        for (int i=0; i<10; i++)
          { if (source.equals(keys[i]))  //---- am I entering "numbers"?
              { if (firstNoIn)
                  { regB.append(String.valueOf(i));
                    display.setText(regB.toString());
                    return;
                  }  // ends the "if" for the second number
                else
                  { regA.append(String.valueOf(i));
                    display.setText(regA.toString());
                    return;
                  }  // ends the "else" for the first number
               }  //---- ends "if" for entering "numbers"
          }   //---- ends "loop" for checking "numbers"
        for (int j=10; j<15; j++)   //---- am I entering "operators"?
          { if ( source.equals(keys[j]) && j!=posEq ) //---- but not "="!!
              { operator = keys[j].charAt(1);
                firstNoIn = true;    // so must have finished the 1st no!!
                return;
              }
          }    //---- ends "loop" for checking "operators"

        if (source.equals(" = "))
          { display.setText(doCalc());
            regA.setLength(0);
            regB.setLength(0);
            firstNoIn = false;
          }
      }  //------------ end of actionPerformed -------------------

    private String doCalc()
      {
        final char BEEP = '\u0007';
        try
          { int A = Integer.parseInt(regA.toString());
            int B = Integer.parseInt(regB.toString());
            switch (operator)
              { case '+': return String.valueOf(A + B);
                case '-': return String.valueOf(A - B); 
                case '*': return String.valueOf(A * B);
                default : return String.valueOf(A / B);
              }
          }
        catch (Exception ouch)
          { System.out.print(BEEP);
            return "     ERROR";
          }
      }  //---------- end of the doCalc() method ------------------
  } //---------------------- end of class NumberCruncher1



+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
import java.awt.*;

class kalk2  // save as kalk2.java
  {
    public static void main (String [] args)
      {
        NumberCruncher2 C = new NumberCruncher2("yummypoos");
      }
  }
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
// General import statements:
import java.awt.*;
import java.awt.event.*;
import java.io.*;

///////////////////////////////////////////////////////////////////////
//                   The NumberCruncher2 class definition            //
///////////////////////////////////////////////////////////////////////
public class NumberCruncher2 extends Frame 
                             implements ActionListener, WindowListener
  {
    class Display extends Canvas
     {
       public void paint(Graphics g)
         { 
           int w = getSize().width; int h = 40;
           g.drawRect(1,1,w-2,h-2);
           g.setColor(Color.magenta);
           g.drawString(coffee, 30, 20);
           g.setFont(new Font("SansSerif", Font.PLAIN, 20));
         } 
       public Dimension getMinimumSize() {return new Dimension(50,50);}
       public Dimension getPreferredSize() {return getMinimumSize();}       
     }

    private Display display = new Display();
    private Button [] nobs = new Button[15];
    private String coffee="Nothing happened";
    static String [] keys = {" 0 "," 1 "," 2 "," 3 "," 4 ",
                             " 5 "," 6 "," 7 "," 8 "," 9 ",
                             " + "," - "," = "," * "," / "};
    private StringBuffer regA = new StringBuffer();
    private StringBuffer regB = new StringBuffer();
    private char operator;
    private boolean firstNoIn = false;

    public NumberCruncher2( String s )
      {
        super(s);
        display.setSize(30,100);
        setBackground(Color.yellow);
        addWindowListener(this);
        setLayout(new GridLayout(2,1));
        add(display);
        Panel pad = new Panel();
        pad.setLayout(new GridLayout(5,3));
        for (int i=0; i<keys.length; i++)
          { nobs[i] = new Button(keys[i]);
            nobs[i].addActionListener(this);
            pad.add(nobs[i]);
          }
        add(pad);
        setSize(150,299);
        show();
      } // --------------- end of constructor

    // ---------- implementing WindowListener methods -----------
    public void windowClosed(WindowEvent evt){}
    public void windowDeiconified(WindowEvent evt){}
    public void windowIconified(WindowEvent evt){}
    public void windowActivated(WindowEvent evt){}
    public void windowDeactivated(WindowEvent evt){}
    public void windowOpened(WindowEvent evt){}
    public void windowClosing(WindowEvent evt){ System.exit(0); }

    public void actionPerformed(ActionEvent evt)
      {
        final int posEq = 12;
        Object source = evt.getActionCommand();
        for (int i=0; i<10; i++)
          { if (source.equals(keys[i]))  //---- am I entering "numbers"?
              { if (firstNoIn)
                  { regB.append(String.valueOf(i));
                    coffee = regB.toString(); display.repaint();
                    //display.setText(regB.toString());
                    return;
                  }  // ends the "if" for the second number
                else
                  { regA.append(String.valueOf(i));
                    coffee = regA.toString(); display.repaint();
                    //display.setText(regA.toString());
                    return;
                  }  // ends the "else" for the first number
               }  //---- ends "if" for entering "numbers"
          }   //---- ends "loop" for checking "numbers"
        for (int j=10; j<15; j++)   //---- am I entering "operators"?
          { if ( source.equals(keys[j]) && j!=posEq ) //---- but not "="!!
              { operator = keys[j].charAt(1);
                firstNoIn = true;    // so must have finished the 1st no!!
                return;
              }
          }    //---- ends "loop" for checking "operators"

        if (source.equals(" = "))
          { coffee = doCalc(); display.repaint();
            //display.setText(doCalc());
            regA.setLength(0);
            regB.setLength(0);
            firstNoIn = false;
          }
      }  //------------ end of actionPerformed -------------------

    private String doCalc()
      {
        final char BEEP = '\u0007';
        try
          { int A = Integer.parseInt(regA.toString());
            int B = Integer.parseInt(regB.toString());
            switch (operator)
              { case '+': return String.valueOf(A + B);
                case '-': return String.valueOf(A - B); 
                case '*': return String.valueOf(A * B);
                default : return String.valueOf(A / B);
              }
          }
        catch (Exception ouch)
          { System.out.print(BEEP);
            return "     ERROR";
          }
      }  //---------- end of the doCalc() method ------------------
  } //---------------------- end of class NumberCruncher2


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