From the javadoc for the java.util.PriorityQueue class:

• "Implementation note: this implementation provides O(log(n)) time for the enqueing (adding) and dequeing (removing) methods"

Recall the difference between O(n) (linear) and O(log(n)) (logarithmic) time:

n	log(n)
8	3
16	4
32	5
...	...
512	9
1024	10

How does java.util.PriorityQueue achieve logarithmic time performance?