title: Adding to ArrayList from separate thread
body: <p>I have a program with 3 threads (excluding the main thread). The first thread moves an object across the window, the second thread checks for object collisions, and the third is supposed to add to the ArrayList of objects periodically. All three of these threads are manipulating the same list of objects (Though the first 2 are not actually changing the list, just the objects inside). However, when the thread meant to add to the list tries to add an object, I receive an error. Is it possible to manipulate an ArrayList from a different thread?</p>