从数组列表中选择随机的唯一项

Question

Say I want to pick 5 random colors from an array list like this one:

static final List<Color> colors = new ArrayList<Color>();

static {
    colors.add(Color.RED);
    colors.add(Color.BLUE);
    colors.add(Color.GREEN);
}

It's pretty easy I can just do this...

static Random random = new Random();

public static Color getRandomColor() {
    return colors.get(random.nextInt(colors.size());
}

But what if I want to pick unique colors which aren't the same? So say I pick RED, how can I make sure to not pick RED again; preferably without removing it from the list, too.

EDIT:

I've found something that works:

Color generatedColor = Theme.randomColor();
for (int i = 0; i < pie.segments.size(); i++) {
    if (generatedColor == pie.segments.get(i).getColor()) {
        generatedColor = Theme.randomColor();
        return;
    }
}
this.color = generatedColor;

However someone suggested I just remove them all and re-add once I've finished generating them all, which method should I go for?

EDIT 2:

After shuffling, I get this: http://i.imgur.com/HPKQNFH.png

Thanks! :)

Answer 1

Use remove method, which return the object at the position and then remove it.

list.remove(int i)

Then your method becomes:

public static Color getRandomColor() {
    return colors.remove(random.nextInt(colors.size());
}

and when the list size is 0, reinsert all the colors.