Programming Forums - help filling array randomly, in a way

I have a little problem with an algorthm. I have to make the game Concentration. It's a game in which tiles are placed face-down in rows on a "concentraction board". Each tile contains a string. For each tile, there is exactly one other tile like that, which is also faced down.

The problem I am having is filling the board up randomly with having only 2 of the each tile in the board. I know there has to be a simple way to do it but my mind justs goes blank. Any help fellows?

public class Tile 

{

    private String name;

 

    public Tile(String name)

    {

         this.name = name;

    }

    public String toString()

    {

        return name;

    }

}

Here is the code for the FooList
A FooList is a class that defines a list of strings and a string length. All strings in a FooList have the same length.

import java.util.ArrayList;

import java.util.Random;

public class FooList 

{

    private final int fooLength;

    private ArrayList<String> availableFoos;

 

    public FooList(int len)

    {

       fooLength = len;

       availableFoos = new ArrayList<String>();

    }

    public String getFoo(int x)

    {

        return availableFoos.get(x);

    }

    public boolean found(String key)

    {

       for(int x = 0; x < availableFoos.size(); x++)

       {

           if(key.equals(availableFoos.get(x)))

               return true;

       }

       return false;

    }

    public void addFoo(String foo)

    {

        if(found(foo) || foo.length() != fooLength)

           return;

        availableFoos.add(foo);

    }

   public String removeRandomFoo()

   {

     Random random = new Random();

     int max = availableFoos.size() - 1;

     int rnd = (random.nextInt() * max);

     String foo = availableFoos.get(rnd);

     availableFoos.remove(rnd);

     return foo;

   }

}

Here's the Board class.

import java.util.ArrayList;

 

public class Board 

{

   private Tile[] gameboard;

   private int size;

   private int rowlength;

   int numberOfTilesFaceUp;

   private FooList possibleTileValues;

 

   public Board(int n, FooList list)

   {

      gameboard = new Tile[n * n];

      size = gameboard.length;

      numberOfTilesFaceUp = 0;

      rowlength = 0;

      possibleTileValues = list;

      fillBoard();

   }

   private void fillBoard()

   {

       //so confused

   }

   public static void main(String args[])

   {  //for debugging purposes

       FooList list = new FooList(4);

       list.addFoo("cats");

       list.addFoo("dogs");

       list.addFoo("bird");

       list.addFoo("mice");

       list.addFoo("fish");

       Board board = new Board(4, list);

   } 

}