Contoh Program Java Calculator

import javax.microedition.midlet.MIDlet;
import javax.microedition.lcdui.*;
public class CALCULATORMIDlet extends MIDlet implements CommandListener, ActionListener{
  private Display display;
  Button n1,n2,n3,n4,n5,n6,n7,n8,n9,n0,plus,minus,mul,div,dot,equal;
  private TextField enter numbers, result;
  private Command enter,back;
 public LoginExample() {
    form = new Form("Sign in");
    userName = new TextField("enter numbers:", "", 30, TextField.ANY);
    password = new TextField("Result:", "", 30, TextField.result);
    cancel = new Command("enter", Command.CANCEL, 2);
    login = new Command("back", Command.OK, 2);
     n7 = new Button("7");
     n7.addActionListener(this);
     n8 = new Button("8");
     n8.addActionListener(this);

     div=new Button("/");
     div.addActionListener(this);
         n4=new Button("4");
         n4.addActionListener(this);
         n5=new Button("5");

         n5.addActionListener(this);
         n6=new Button("6");

         n6.addActionListener(this);
         mul=new Button("*");
         mul.addActionListener(this);

         n1=new Button("1");
         n1.addActionListener(this);

         n2=new Button("2");
         n2.addActionListener(this);
         n3=new Button("3");
         n3.addActionListener(this);
         minus=new Button("-");
         minus.addActionListener(this);
         dot=new Button(".");        

dot.addActionListener(this);
         n0=new Button("0");

         n0.addActionListener(this);
         equal=new Button("=");

         equal.addActionListener(this);
         plus=new Button("+");


         plus.addActionListener(this);
         add(panel,BorderLayout.CENTER);
      }
       public void actionPerformed(ActionEvent ae)


         {
      if(ae.getSource()==n1) assign("1");

      else if(ae.getSource()==n2) assign("2");
      else if(ae.getSource()==n3) assign("3");
      else if(ae.getSource()==n4) assign("4");
      else if(ae.getSource()==n5) assign("5");

      else if(ae.getSource()==n6) assign("6");
      else if(ae.getSource()==n7) assign("7");

      else if(ae.getSource()==n8) assign("8");
      else if(ae.getSource()==n9) assign("9");
      else if(ae.getSource()==n0) assign("0");
      else if(ae.getSource()==dot)
            {
             if(((result.getText()).indexOf("."))==-1)

                result.setText(result.getText()+".");
           }

          else if(ae.getSource()==minus)
             {
             preRes=Double.parseDouble(result.getText());
             lastCommand="-";

             result.setText("0");
             }


      else if(ae.getSource()==div)
             {

             preRes=Double.parseDouble(result.getText());
             lastCommand="/";
             result.setText("0");
             }

      else if(ae.getSource()==equal)
             {


             secVal=Double.parseDouble(result.getText());
             if(lastCommand.equals("/"))

                  res=preRes/secVal;
             else if(lastCommand.equals("*"))

                  res=preRes*secVal;
             else if(lastCommand.equals("-"))

                  res=preRes-secVal;
             else if(lastCommand.equals("+"))

                  res=preRes+secVal;
             result.setText(" "+res);

             lastCommand="=";
             }

      else if(ae.getSource()==mul)
             {

              preRes=Double.parseDouble(result.getText());
              lastCommand="*";

              result.setText("0");
              }

      else if(ae.getSource()==plus)
              {

              preRes=Double.parseDouble(result.getText());
              lastCommand="+";
              result.setText("0");
              }
}

      private static void assign(String no)
        {
         if((result.getText()).equals("0"))
            result.setText(no);
          else if(lastCommand=="=")

           {
            result.setText(no);

            lastCommand=null;
           }
          else
            result.setText(result.getText()+no);

         }
 }

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