No double picks in image Array Processing 3.0 - arrays

Question

i've been trying to make a program that takes (for example) 3 cards at random.
But i don't want my program to grab the same card twice, so that means it can't have duplicates, but i don't know how to do this with a image Array.
String[] card = {
"Aclubs.png",
"2clubs.png",
"3clubs.png",
};
PImage[] cards = new PImage [card.length];
void setup() {
size(1000,1000);
randomCards();
drawCards();
}
int randomCards() {
int i = (round(random(0,2)));
cards[i] = loadImage(card[i]);
return i;
}
void drawCards() {
for (int g = 0; g < 12000; g = g+round((displayWidth * 0.9))/12) {
image(cards[randomCards()], 25+g, 50);
}
}

Answer 1

Instead of using an array, use an ArrayList. Then remove the cards you use. Here's a small example:
ArrayList<String> things = new ArrayList<String>();
things.add("cat");
things.add("dog");
things.add("lizard");
while (!things.isEmpty()) {
int index = int(random(things.size()));
String thing = things.remove(index);
println(thing);
}
Of course, this isn't the only way to do it. You could use a Java Set, or you could use a data structure that holds what you've already picked, or you could store all of the options in a data structure, then shuffle it, then just chose from an index that you increment. Or you could use one of the array functions in the reference to do it.
It's hard to answer general "how do I do this" type questions. Stack Overflow is designed for more specific "I tried X, expected Y, but got Z instead" type questions. So you really should get into the habit of trying things out first. Ask yourself how you would do this in real life, then look at the reference to see if there are any classes or functions that would help with that. Break your problem down into smaller pieces. Write down how you would do this in real life, in English. Pretend you're handing those instructions to a friend. Could they follow your instructions to accomplish the goal? When you have those instructions written out, that's an algorithm that you can start thinking about implementing in code. Staring at code you've already written won't get you very far. Then when you do get stuck, you can ask a more specific question, and it'll be a lot easier to help you.