Concurrency.. ^^

[Mads]

What if you just use a for loop instead, and check for null objects? Would that not (although while being a cheap solution), stop throwing you those exceptions?

[Regenuluz]

@sproingie
Arh, well, I am synch’ing it myself But I’ll make a note to remember to not mix concurrent collections and internally-synch’ed methods.

@Mads
It’s not null pointers that’s causing that exception. It’s because elements are being added or removed from the list while it’s being iterated through.

[cylab]

@Regenuluz

@Mads
It’s not null pointers that’s causing that exception. It’s because elements are being added or removed from the list while it’s being iterated through.

He means a for-loop with an index and a getter. The CME is only thrown when using for(x:y) loops or Iterators. So his suggestion is

for(int i=0; i<entitiesToTick.size(); i++)
{
    Entity e=entitiesToTick.get(i);
    if(e!=null) e.tick();
}

unfortunately that won’t work either, because of:

public Object get(int index)

Returns the element at the specified position in this list.

Parameters:
    index - index of element to return. 
Returns:
    the element at the specified position in this list. 
Throws:
   [b] IndexOutOfBoundsException - if the index is out of range (index < 0 || index >= size()).[/b]

so if an element gets removed while iterating over it, an IOOBE is thrown. Other than that, this loop could lead to missed entities or double calls to tick() on the same entity.