title: Crash when trying to remove object from ArrayList
body: <p>im having a problem i havent been able to figure out a solution to. Im making a small game where the object in _sballs ArrayList will be deleted if collided with another object called ball.
  the problem i've encountered is that when the collision occur and when i attempt to remove the object from the ArrayList, the application crashes.</p>
  
  <pre><code>for(GObject sballgraphic : _sballs){
              Coordinates sballcoords = sballgraphic.getCoords();
              if(coords.getY() - coords._height &gt; sballcoords.getY() + sballcoords._height &amp;&amp; coords.getX() - coords._width &gt; sballcoords.getX() + sballcoords._width){
                  _sballs.remove(sballgraphic);
              }
          }
  </code></pre>
  
  <p>So the code compares the balls coordinates with all the sballs objects to check if there is a collision, then tries to remove the sball.</p>
  
  <p>What is the problem here? :)</p>