Interview Question

HashMap vs TreeMap?

HashMap uses hashing without order; TreeMap keeps sorted keys.

💡 Concept ✅ Quick Revision ☕ Java

Answer

HashMap is a hash-table Map; TreeMap is a sorted NavigableMap based on a red-black tree. • HashMap has no ordering guarantee. • TreeMap orders keys by natural ordering or a Comparator. • HashMap gives average constant-time get and put; TreeMap gives logarithmic operations.

Example

Code

var map = new java.util.TreeMap<Integer, String>();
map.put(2, "two"); map.put(1, "one");
System.out.println(map.keySet());

Output

[1, 2]

Quick Revision

HashMap uses hashing without order; TreeMap keeps sorted keys.

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