TreeMap

Basics

• TreeMap is ordered by Keys
• put(), get(), remove() all cost O(logN) in the worst scenario
• Iteration order predictable
• Allows only Values to be null, Keys cannot be null

TreeMap vs HashMap

• TreeMap are naturally sorted by order of key, HashMap is not:

TreeMap<Integer, Integer> tm = new TreeMap<>();

tm.put(3, 1);

tm.put(2, 2);

tm.put(1, 10);

tm.put(-100, 2);

tm.values(); //[2, 10, 2, 1]

HashMap<Integer, Integer> hm = new HashMap<>();

hm.put(3, 1);

hm.put(2, 2);

hm.put(1, 10);

hm.put(-100, 2);

hm.values(); // [10, 2, 1, 2]