This is quite a long Applet and involves many Classes which have been developed in previous pages.

It will repay some study.

If you can modify the Applet successfully you will learn a lot.

Nothing new here, just a bit longer than usual.

Call the method that generates a question.

Notice that the main logical structure is put here, the actual processing parts are handled by separate methods for convenience.

Answered is a flag or sentinel - an SL mastery aspect.

Use a try block because the BinaryTextFiedl will throw an exception if the String typed into it is not a valid binary byte.

We can then use our custom exception messages.

We've used a method here because it will make it easier to extend the example to Binary Decimal conversions or mixtures of both.

Start with an empty String

Generate random number 0 - 499

3/5 of the numbers will be 1's on average.

Math.random returns a long primitive in the range 0 >= x > 1.0

(int) is a cast used to convert a long to an int.

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

/**
* Implements a test for simple unsigned binary numbers
* It uses BinaryException and BinaryTextField Classes
*
* @author Mr J
* @version 20040221
*/

public class BinaryQuiz extends Applet implements ActionListener
{
   // Using our new TextField objects
   BinaryTextField numberB = new BinaryTextField(20);
   IntegerTextField numberD = new IntegerTextField(20);
   // awt interface objects
   Label messages = new Label("Messages appear here...................");
   Button answer = new Button("Check Answer");
   Button again = new Button("Try again");
   // check if they have answered the question yet
   boolean answered = false;
   /**
   * Add objects to Applet
   */
   public void init()
   {
     // set up panels for the TextFields and Buttons
     Panel fieldPanel = new Panel();
     fieldPanel.setLayout(new GridLayout( 2, 1 ) );
     Panel buttonPanel = new Panel();
     buttonPanel.setLayout(new GridLayout( 1, 2 ) );
     // add to panels
     fieldPanel.add(numberB);
     fieldPanel.add(numberD);
     buttonPanel.add(answer);
     buttonPanel.add(again);
     // action Listeners for the buttons
     answer.addActionListener(this);
     again.addActionListener(this);
     // set up the interface
     add(fieldPanel);
     add(buttonPanel);
     add(messages);
     // start off with a new question
     generateQuestion();
   }
   /**
   * When the press button is pressed the answer is checked
   * When the again button is pressed a new number is generated
   *
   * @param e the event that generated the call to this method
   */
   public void actionPerformed(java.awt.event.ActionEvent e)
   {
     if (e.getSource() == answer)
     {
       if (processAnswer())
       {
         messages.setText("Correct, well done!");
         answered = true;
       }
     }  
     else
     {
       if (answered)
       {
         generateQuestion();
         answered = false;
       }
       else
       {
         messages.setText("But you haven't answered this one yet!");
       }
     }
   }
  /**
  * Process the answer
  *
  * @return true if the question was answered correctly
  */
   private boolean processAnswer()
   {
     try
     {
       // numberB holds the answer, check it, an exception will be thrown
       // if the answer is not valid binary
       if (numberD.getInteger() == numberB.convert())
       {
         return true;
       }
       else
       {
         messages.setText("Sorry, please try again");
       }
     }
     catch(BinaryTextFieldException btfe)
     {
       messages.setText(btfe.getMessage());
     }
     return false;
   }
   /**
   * Generate a question (integer value)
   * disable the TextField holding the question
   */
   private void generateQuestion()
   {
     // decimal to Binary conversion
     // Generate decimal number
     numberD.setText(generateDecimal());
     numberD.setEditable(false);
  }
   /**
   * This method generates a binary byte - useful if you want to
   * reverse the quiz (hint, hint)
   * It returns more 1's than zeros on average
   *
   * @return java.lang.String
   */
   private String generateBinary()
   {
     String s = "";
     int r, p;

     for (p = 0; p < 8; p++)
     {
       r = (int) (Math.random() * 500);
       if( r >= 300)
       {
         s = s + "0";
       }
       else
       {
         s = s + "1";
       }
     }
     return s;
   }
   /**
   * This method generates an int in the range 0 to 255
   *
   * @return a representation of the integer
   */
   public String generateDecimal()
   {
     return ("" + (int) (Math.random() * 256));
   }
}

Exercise:

The quiz needs improvement in the following areas:

• It should keep score for a person and only give the results at the end of the quiz
• It should test (perhaps randomly) binary to decimal conversion as well

Related: [ Java Home | previous:Inheritance ]

Applet that runs a binary conversion quiz.

You have to enter a valid , 8-bit binary byte .

For example , if you are asked to convert 2, enter 00000010, not just 10.

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