LinkedHashMap in Java

LinkedHashMap is a class in Java that extends the HashMap class and maintains a linked list of the entries in the map. This linked list is used to maintain the order of insertion of the entries. Thus, a LinkedHashMap provides the functionality of a HashMap along with the ability to maintain the order of insertion of its entries.

Here is an example of how to create a LinkedHashMap in Java:

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

In this example, a new LinkedHashMap is created with keys of type String and values of type Integer. The put method is used to add entries to the map. The order of insertion is maintained, so the keys “one”, “two”, and “three” will be in the same order as they were inserted.

LinkedHashMap provides several methods to access and modify the entries in the map. Some of the most commonly used methods are:

1. put(K key, V value): This method is used to add a new entry to the map with the specified key and value.

linkedHashMap.put("four", 4);

2. get(Object key): This method is used to get the value associated with the specified key in the map.

Integer value = linkedHashMap.get("two");

3. remove(Object key): This method is used to remove the entry with the specified key from the map.

linkedHashMap.remove("three");

linkedHashMap.clear();

Set<String> keys = linkedHashMap.keySet();

Collection<Integer> values = linkedHashMap.values();

Set<Map.Entry<String, Integer>> entries = linkedHashMap.entrySet();