remove array from random when used

Question

I'm not certain if the title is the right way to word what I'm asking, sorry if it's not, but what I'm trying to do is create a memory match game using GUI. I have an array, and I've got the button printing an element from the array at random, but, the issue is, that I can have the same element printing multiple times. Is there a way to remove that element from being selected once it's used? If there isn't a way to do that, any ideas on how I could go about getting it to use each element only once? This is my current code:

    package MemoryMatching;
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.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;

public class MemoryGUI extends JFrame implements MemoryMatch, ActionListener{
    JPanel mainPanel, boardPanel;
    JButton [][] gridButtons = new JButton[3][4];
    char cardArray[] = new char[12];
    int numInPlay;

    public MemoryGUI(){
        cardArray[0] = 'A';
        cardArray[1] = 'A';
        cardArray[2] = 'B';
        cardArray[3] = 'B';
        cardArray[4] = 'C';
        cardArray[5] = 'C';
        cardArray[6] = 'D';
        cardArray[7] = 'D';
        cardArray[8] = 'E';
        cardArray[9] = 'E';
        cardArray[10] = 'F';
        cardArray[11] = 'F';
        mainPanel = new JPanel();
        mainPanel.setLayout(new BorderLayout());
        boardPanel = new JPanel();
        boardPanel.setLayout(new GridLayout(4,3));
        setBoard();
        mainPanel.add(boardPanel, BorderLayout.CENTER);
        add(mainPanel);
    }
    @Override
    public void actionPerformed(ActionEvent e) {
        JButton btnClicked = (JButton) e.getSource();
        btnClicked.setEnabled(false);
        char randomChar = cardArray[(int)new Random().nextInt(cardArray.length)];

        btnClicked.setText(""+ randomChar);
        faceUp();

    }

    @Override
    public void setBoard() {
        for(int x = 0; x < cardArray.length; x++) {

        }
        for(int row=0; row<gridButtons.length; row++){
            for(int col=0; col<gridButtons[row].length;col++){
                gridButtons[row][col] = new JButton();
                gridButtons[row][col].addActionListener(this);
                gridButtons[row][col].setText("No peeking");
                boardPanel.add(gridButtons[row][col] );
                faceDown();
            }
        }
    }

    @Override
    public void isWinner() {
        // TODO Auto-generated method stub

    }
    @Override
    public void isMatch() {


    }
    @Override
    public void faceUp() {
        for(int x = 0; x < cardArray.length; x++) {
            for(int y = 0; y < cardArray[x]; y++) {

            }
        }
    }
    @Override
    public void faceDown() {


    }
}

what I'm currently getting is something like A B A A F B F D D E F C rather than: B A C D E F A B C F E D The first example having three A and one C, rather than two of each as in the second example. If possible I'd like to not be given the code outright, but a push towards the right direction.

score 0 · Accepted Answer · answered Oct 13 '17 at 15:07

0

A simple solution: don't use an array.

Instead, use a List<Integer> and shuffle that list. Then simply use the last element of the list for your purpose - and then remove the last element from the list; and shuffle again.

Of course, you could also write a bit of code to keep track of all indexes that you already used, and keep asking for random indexes until you get one that wasn't used before.

answered Oct 13 '17 at 15:07

GhostCat

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I haven't been able to get the text to display properly, but using List instead of Array makes me feel much closer to the desired result. – HoneybunHero Oct 13 '17 at 17:15

score 0 · Answer 2 · answered Oct 13 '17 at 15:21

For your code, I think the following code would do the trick.

array = ArrayUtils.removeElement(array, element)

If you really want to use an array, look into Fisher–Yates shuffle for random shuffling of an array.

However, my recommendation would be to not use an array. Use a list as the other answer suggested.

remove array from random when used

2 Answers2