Need help with creating a random array.

[Thomas Mullane]

So first I had to create an insert method to place tracks into an array.. Got that easy enough.. Next I have to randomly mix up that array... Can get some of that but my last track is being duplicated a lot of the time.. I heed help to stop this! Here is my code!

public class wk
{
    public void play(boolean random)
    {
        Track[] randNumbers = new Track[list.length];
        int ran = 0,c=0;
        this.randNumbers = this.list;
        Track temp;
        boolean ans =false;
        if(random == false){
            display();
        }else{
            for (int j = this.list.length-1; j>=0; j--) { 
                if(randNumbers.length != this.list.length-1){
                        ran = (int)(Math.random()*j);
                        temp = this.randNumbers[ran];
                        this.randNumbers[ran] = this.randNumbers[j];
                        this.randNumbers[j] = temp;
                }
            }
        }
        entryCount=entryCount+3;
    }
}

list is the original array that the tracks were inserted into.
entryCount is the list length.

[Stephan van Hulst]

Hi Thomas,

Why don't you just use Lists instead of arrays? You will also be able to simply use the Collections.shuffle() method.

[Jesper de Jong]

The standard Java library already has a method to shuffle a List: Collections.shuffle(list). If you need to shuffle an array, you can use Arrays.asList(array) to wrap the array as a list.

So to shuffle your array of Track objects you could just do:

Collections.shuffle(Arrays.asList(randNumbers));

If you need to implement this yourself (for example because it's homework and you're supposed to implement it yourself), see Fisher–Yates shuffle for an explanation of a good and simple shuffling algorithm.