The JavaDoc for the ArrayList() constructor says

    Constructs an empty list with an initial capacity of ten.

but in fact it creates an ArrayList whose elementData is an Object[0]. Adding an element to the ArrayList causes ensureCapacity() to replace elementData with an Object[DEFAULT_CAPACITY]. Compare that to calling ArrayList(10) where I can add an element without allocating a new elementData.

I found this by noticing that calling ArrayList.add(E) caused an allocation and a garbage collection in a place where I was hoping to avoid a garbage collection. Using Array(10) solves my problem. I think either the JavaDoc for ArrayList() is misleading, or the implementation does not match the JavaDoc.