在Java中使用带有增强的for循环的迭代器？

Question

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 (ie 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.

Answer 1

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();

Answer 2

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.