The constructor WeakHashMap(Map<? extends K, ? extends V> m) delegates construction as
        this(Math.max((int) (m.size() / DEFAULT_LOAD_FACTOR) + 1,
                DEFAULT_INITIAL_CAPACITY),
             DEFAULT_LOAD_FACTOR);

If m.size() is large (>= 1610612672) then the first argument of Math.max() becomes negative due to integer overflow, and WeakHashMap with default capacity is created.

While it is mostly unnoticeable, it is unnecessary.