CODEWITHSUNDEEP
javaloopsfor-loopiterator
user3304654
user3304654

Reputation: 85

Using an iterator with an enhanced for loop in Java?

Okay so in my project for class I'm looking through an ArrayList of my class "Sprite" with an enhanced for loop, and I occasionally need to delete the Sprite that I'm looking at. I'm told I can do this safely (i.e. not deleting the Sprite I'm currently looking at) with Iterators. I looked it up on Oracle's java documentation but I don't really understand it..

Here's my method:

public void forward() {
    for (Sprite s : sprites) {
        s.move();
        for(Sprite x : sprites){
            if(s!=x && s.overlaps(x)){                  
                if(s instanceof Razorback && x instanceof Opponent){
                    x.hit();
                }
                if(x instanceof Razorback && s instanceof Opponent){
                    s.hit();
                }
            }

        }
        if(s.shouldRemove())
            sprites.remove(s);

    }

}

if(s.shouldRemove()) is where I need to implement an iterator. If shouldRemove() return true, s needs to be removed from the ArrayList.

Upvotes: 7

Views: 14726

Answers (2)

Tagir Valeev
Tagir Valeev

Reputation: 100169

In addition to @Codebender answer: to limit the scope of the iterator variable, you can use plain for loop:

for(Iterator<Sprite> it = sprites.iterator(); it.hasNext(); ) {
    Sprite s = it.next();

    ...
    if (s.shouldRemove())
        it.remove();
}

This way the it variable is undefined after the loop.

Upvotes: 13

Codebender
Codebender

Reputation: 14471

You need to loop (and remove) using the iterator itself.

for (Sprite s : sprites) {

should be changed to,

Iterator<Sprite> it = sprites.iterator();
while (it.hasNext()) {
    Sprite s = it.next();

And then your if condition will be,

if (s.shouldRemove())
    it.remove();

Upvotes: 11

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