How does the behavior and features of HashMap differ from LinkedHashMap in Java?

HashMap and LinkedHashMap in Java differ as follows:

• HashMap stores key-value pairs without any guarantee of order. The order of elements may change when adding or removing entries.

• LinkedHashMap extends HashMap and maintains the insertion order of elements. This means that when iterating, elements will be returned in the order they were added.

Features:

• LinkedHashMap is slightly slower due to maintaining a linked list for order.
• LinkedHashMap can be used to implement caches with removal based on access order.

Example:

Map<String, Integer> hashMap = new HashMap<>();
hashMap.put("one", 1);
hashMap.put("two", 2);
hashMap.put("three", 3);

Map<String, Integer> linkedHashMap = new LinkedHashMap<>();
linkedHashMap.put("one", 1);
linkedHashMap.put("two", 2);
linkedHashMap.put("three", 3);

System.out.println("HashMap: " + hashMap.keySet());
System.out.println("LinkedHashMap: " + linkedHashMap.keySet());

Output:

HashMap: [two, one, three]
LinkedHashMap: [one, two, three]

Thus, if the order of elements is important, it is recommended to use LinkedHashMap.