Update AbstractNodeQueue.java

Avoid spinning on head when a peek/poll observes a null next but the queue is not empty.
Update AbstractNodeQueue.java

language language....
Fix isEmpty() and count()

isEmpty() need not rely on peek(which is intended for consumer use) and instead compare head to tail.
count() should stop counting at max int to avoid wrap.
Fixe documentation to state consumer only access is allowed to poll/peek/peekNode/pollNode
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Merge pull request #15596 from nitsanw/master

Update AbstractNodeQueue.java to avoid redundant reads of head in peekNode