What are the differences between HashMap and TreeMap in Java?

What are the differences between HashMap and TreeMap in Java?

HashMap is unordered and allows null keys, while TreeMap is ordered and does not allow null keys. Would you like examples?

Yes, please provide examples of both.

Sure! Here's a HashMap example:

HashMap<String, Integer> map = new HashMap<>();
map.put("A", 1);
map.put("B", 2);
System.out.println(map);

And for TreeMap:

TreeMap<String, Integer> treeMap = new TreeMap<>();
treeMap.put("A", 1);
treeMap.put("B", 2);
System.out.println(treeMap);

What are the performance differences between them?

HashMap has O(1) time complexity for get and put operations, while TreeMap has O(log n) due to its sorted nature.