Removing object from ArrayList in for each loop

Question

I would like to remove an object from an ArrayList when I'm done with it, but I can't find way to do it. Trying to remove it like in the sample code below doesn't want to work. How could I get to the iterator of current px object in this loop to remove it?

for( Pixel px : pixel){  [...]   if(px.y > gHeigh){      pixel.remove(pixel.indexOf(px)); // here is the thing      pixel.remove(px); //doesn't work either   } } 

Answer 1

You can't, within the enhanced for loop. You have to use the "long-hand" approach:

for (Iterator<Pixel> iterator = pixels.iterator(); iterator.hasNext(); ) {   Pixel px = iterator.next();   if(px.y > gHeigh){     iterator.remove();   } } 

Of course, not all iterators support removal, but you should be fine with ArrayList.

An alternative is to build an additional collection of "pixels to remove" then call removeAll on the list at the end.

Answer 2

Using java-8 and lamdba expressions, the method removeIf has been introduced for collections.

Removes all of the elements of this collection that satisfy the given predicate.

So it will only take one line :

pixels.removeIf(px -> px.y > gHeigh);