V computeIfAbsent(K key, Function mappingFunction) It is used to compute a mapping for the specified key and its current mapped value (or null if there is no current mapping). V compute(K key, BiFunction remappingFunction) It returns the Set view containing all the keys and values. It returns the Set view containing all the keys. It removes the specified values with the associated specified keys from the map. It is used to delete an entry for the specified key. It inserts the specified value with the specified key in the map only if it is not already specified. It is used to insert the specified map in the map. It is used to insert an entry in the map. TreeMap is the implementation of Map and SortedMap. LinkedHashMap is the implementation of Map. HashMap is the implementation of Map, but it doesn't maintain any order. HashMap and LinkedHashMap allow null keys and values, but TreeMap doesn't allow any null key or value.Ī Map can't be traversed, so you need to convert it into Set using keySet() or entrySet() method. The hierarchy of Java Map is given below:Ī Map doesn't allow duplicate keys, but you can have duplicate values. There are two interfaces for implementing Map in java: Map and SortedMap, and three classes: HashMap, LinkedHashMap, and TreeMap. A Map contains unique keys.Ī Map is useful if you have to search, update or delete elements on the basis of a key. Each key and value pair is known as an entry. A map contains values on the basis of key, i.e.
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