TreeMap vs PriorityQueue

Comparison

Category	TreeMap	PriorityQueue
Implementation	Uses Red-Black tree	Uses Min (max) tree
Remove Time Complexity	O(log(n))	O(log(n))
Insert Time Complexity	O(log(n))	O(log(n))
Duplicates	No	Yes
Search Time Complexity	O(log(n))	O(n)

When to use PriorityQueue?

As the above comparison shows, when you need duplicates and when you don't care about finding a particular elements by key, you should use this.

When to use TreeMap?

Again, as the comparison shows, when you need duplicates and when you need to find an element based on a particular key, use this. There are ways to put duplicates into TreeMap using a custom Comparator, but try to avoid that as it breaks the general understanding of the TreeMap for users.