RFR 8206123 : ArrayDeque created with default constructor can only hold 15 elements

[Ivan Gerasimov]

Hello!

The spec states that an ArrayDeque created with the default constructor 
should be able to hold 16 elements.

https://docs.oracle.com/javase/10/docs/api/java/util/ArrayDeque.html#%3Cinit%3E()
"""
Constructs an empty array deque with an initial capacity sufficient to 
hold 16 elements.
"""

In the constructor an array of size 16 is created:
         elements = new Object[16];

However, one element must always be null:
     /**
      * The array in which the elements of the deque are stored.
      * All array cells not holding deque elements are always null.
      * The array always has at least one null slot (at tail).
      */
     transient Object[] elements;

which leaves us space for only 15 elements, contrarily to what the spec 
promises.


Would you please help review a trivial fix?

BUGURL: https://bugs.openjdk.java.net/browse/JDK-8206123
WEBREV: http://cr.openjdk.java.net/~igerasim/8206123/00/webrev/

Thanks in advance!

-- 
With kind regards,
Ivan Gerasimov