Calculator Solution

"Clean" Code for the Calculator Exercise

import java.awt.*;
import java.applet.Applet;

public class Calculator extends Applet {

     private Button makeButton(String label, Color color)
     {
          Button b = new Button(label);
          b.setBackground (color);
          b.setFont (new Font ("Courier", Font.BOLD, 10));
          return b;
     }

     private Panel makePanel (LayoutManager lm, Color c)
     {
          Panel p = new Panel( );
          p.setLayout (lm);
          p.setBackground (c);
          return p;
     }

     private void makeButtons( )
     {
          Color lightRed = new Color(255,100,100);
          Color lightBlue = new Color(100,100,255);
          Color yellow = new Color(255,255,0);

          c = makeButton("C", lightRed);
          eq = makeButton("=", lightBlue);
          div = makeButton("/", lightBlue);
          times = makeButton("*", lightBlue);
          d7 = makeButton("7", yellow);
          d8 = makeButton("8", yellow);
          d9 = makeButton("9", yellow);
          minus = makeButton("-", lightBlue);
          d4 = makeButton("4", yellow);
          d5 = makeButton("5", yellow);
          d6 = makeButton("6", yellow);
          plus = makeButton("+", lightBlue);
          d1 = makeButton("1", yellow);
          d2 = makeButton("2", yellow);
          d3 = makeButton("3", yellow);
          d0 = makeButton("0", yellow);
          dp = makeButton(".", yellow);
          eq2 = makeButton("=", lightBlue);
     }

     public void init( )
     {
          background = new Color(200,255,255);
          this.setLayout(new FlowLayout(FlowLayout.CENTER,4,1));

          result = new Label("0.00000", Label.RIGHT);
          result.setBackground(new Color(255,255,255));
          add(result);
          makeButtons( );

          row1 = makePanel(new FlowLayout(FlowLayout.LEFT,4,2),background);
          row1.add(c);
          row1.add(eq);
          row1.add(div);
          row1.add(times);

          row2 = makePanel(new FlowLayout(FlowLayout.LEFT,4,2),background);
          row2.add(d7);
          row2.add(d8);
          row2.add(d9);
          row2.add(minus);

          row3 = makePanel(new FlowLayout(FlowLayout.LEFT,4,2),background);
          row3.add(d4);
          row3.add(d5);
          row3.add(d6);
          row3.add(plus);

          add(row1);
          add(row2);
          add(row3);

          p12 = makePanel(new BorderLayout(2,2), background);
          p12.add("West",d1);
          p12.add("East",d2);

          p120 = makePanel(new BorderLayout(2,2), background);
          p120.add("North",p12);
          p120.add("South",d0);

          p3p = makePanel(new BorderLayout(2,2), background);
          p3p.add("North",d3);
          p3p.add("South",dp);

          p3peq = makePanel(new BorderLayout(2,2), background);
          p3peq.add("West",p3p);
          p3peq.add("East",eq2);

          add(p120);
          add(p3peq);

          setBackground(background);
     }

     public void start ()
     {
          setSize(row1.getSize( ).width,8*d1.getSize( ).height);
          validate( );   // refreshes the applet
     }

     public Panel row1, row2, row3, p12, p120, p3p, p3peq;

     private Button c, eq, div, times,
                           d7, d8, d9, minus,
                           d4, d5, d6, plus,
                           d1, d2, d3,
                           d0, dp,       eq2;
     private Color background;
     private Label result;
}