使用while循环创建Java GUI的问题

Question

I am creating a java GUI which is a fortune teller. The GUI will spit out one of twelve fortunes every time you click the "get my fortune" button, the strings will never repeat back to back, can can repeat later after other strings have gone before it. I have made already for the most part. But now I am having some trouble creating the while loops to display the strings without repeating. I have looked at my book which didn't really help. If you guys could point me in the right direction,it would be much appreciated. Thanks! I entered all of the code so you can see the variables used. But my question starts at class RndButtonListener.

package FortuneTellerRunner;
import java.awt.BorderLayout;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.Random;
import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;


/**
 *
 * @author a3cal_000
 */
class FortuneTellerFrame extends JFrame
{
  final private JPanel mainPnl, titlePnl, displayPnl, buttonPnl, imagePnl;
  final private JButton quitBtn, rndBtn;
  final private JLabel titleLbl, iconLbl;
  final private JTextArea displayTa;
  final private JScrollPane scroller; 
  public String[] fortune = new String [12];
  int newIndex, oldIndex;
  private static final int HEIGHT = 250;
  private static final int WIDTH = 450;

public FortuneTellerFrame()
{
  setSize(WIDTH, HEIGHT);  
  setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

  mainPnl = new JPanel();
  mainPnl.setLayout(new BorderLayout());

  displayPnl = new JPanel();
  buttonPnl = new JPanel();
  titlePnl = new JPanel();
  ImageIcon icon = new ImageIcon("FortuneTellerIcon.JPEG");
  iconLbl = new JLabel(icon);  
  titleLbl = new JLabel("Fortune Teller!");
  displayTa = new JTextArea();  
  imagePnl = new JPanel();
  scroller = new JScrollPane();
  // Create the layout of the title panel
  titlePnl.setLayout(new GridLayout(2,1));

  add(mainPnl);

  // Set the label to the panel.
  titlePnl.add(titleLbl);
  titlePnl.add(iconLbl);  


    // add the panel to the main panel.
    mainPnl.add(titlePnl, BorderLayout.NORTH);
    mainPnl.add(scroller, BorderLayout.CENTER);
    mainPnl.add(displayTa, BorderLayout.CENTER);       

    // Create the "Get my fortune button.
    rndBtn = new JButton("Get My Fortune!");
    quitBtn = new JButton("Quit");



    // Add the buttons to the buttonPnl in grid layout.
    buttonPnl.add(rndBtn);
    buttonPnl.add(quitBtn);

    // Create the grid layout for the button panel.
    buttonPnl.setLayout( new GridLayout(1, 2));

    // Add the button panel to the grid layout, South.
    mainPnl.add(buttonPnl, BorderLayout.SOUTH);    




    ActionListener listener = new RndButtonListener();
    rndBtn.addActionListener(listener);
    quitBtn.addActionListener(listener);

}


class RndButtonListener implements ActionListener
{
    public void actionPerformed(ActionEvent evt)
    {
        fortune[0] = "He who throws dirt is losing ground.";
        fortune[1] = "You will find the love of your life in food.";
        fortune[2] = "Do or do not, there is no try.";
        fortune[3] = "Tomorrow is a better day to try anything of importance.";
        fortune[4] = "Life's not about how hard you can hit, but how hard you can get hit and keep moving forward.";
        fortune[5] = "You can't be late until you show up.";
        fortune[6] = "If you think things can't get worse it's probably only because you lack sufficent imagination.";
        fortune[7] = "If youre at the top it means you have further to fall.";
        fortune[8] = "Even in last place, youre still in the race.";
        fortune[9] = "The road to riches is paved on the failures of others.";
        fortune[10] = "If you feel like your going no where, get off the treadmill.";
        fortune[11] = "Thinking about going to the gym is just as good as going.";       

        Random rnd = new Random(fortune.length);
        do
        {
        newIndex = rnd.nextInt(fortune.length);

        }
          while(newIndex == oldIndex);

        do
        {
            System.out.println(fortune[newIndex]);

            displayTa.append(fortune[newIndex] + "||");
            displayTa.updateUI();
            mainPnl.updateUI();
            oldIndex = newIndex;

        } 
            while(newIndex != oldIndex);

        class QuitButtonListener implements ActionListener
        {
            public void actionPerformed(ActionEvent evt)
            {
                System.exit(0);
            }        

        }

     }
 }

}

Answer 1

The basic problem is you are re-creating the Random with the same seed each time, which is generally creating the same random sequence over and over again.

Instead try using...

do {
    newIndex = (int) Math.round(Math.random() * (fortune.length - 1));
} while (newIndex == oldIndex);

You also don't need the second loop, it's just clutter that confuses the situation.

You may also find that...

 displayTa.append(fortune[newIndex] + "\n");

produces nicer output (IMHO)

You may also wish to take a look at How to use Scroll Panes

Answer 2

Your program run fine, but this is a problem, fortune.length is a random seed which return me only 6 and 8 when I later called Random.nextInt().

Random rnd = new Random(fortune.length);

Do it this way

Random rnd = new Random();

and also consider the formatting solution given by MadProgrammer.

Answer 3

Random() gives you same number pattern. Try Random(System.currentTimeMillis()). It uses current time as seed, so you can get real random numbers.

Answer 4

I did something similar to this just today, so let's see if I can remember... I made an ArrayList of type int of how many items I had (fortunes)

ArrayList<Integer> fortuneSeq = new ArrayList<Integer>();

Then add in some numbers starting from 0 to code for the fortunes.

for(int i = 0; i < fortune.length; i++) {
    fortuneSeq.add(i);
}

Then I used the shuffle() method from the Collections class to randomize the list.

Collections.shuffle(fortuneSeq);

After that, just loop through to access the fortunes.

for(int i = 0; i < fortune.length; i++) {
    System.out.println(fortune[fortuneSeq.get(i)]);
    //...
}

Edit: Silly autocorrect, you don't like programmers.

Edit: Fixed some furtunes instead of fortunes and fixed println statement.