#Method map update#
#Method map code#

Static Comparator> comparingByKey(Comparator cmp) It returns a comparator that compare the objects in natural order on key. It is used to compare the specified object with the other existing objects.

It is used to replace the value corresponding to this entry with the specified value. It provides methods to get key and value. It returns a collection-view of the map, whose elements are of this class. So we will be accessed it by Map.Entry name. This method returns the number of entries in the map.Įntry is the subinterface of Map. It returns a collection view of the values contained in the map. It replaces each entry's value with the result of invoking the given function on that entry until all entries have been processed or the function throws an exception. It replaces the old value with the new value for a specified key. It replaces the specified value for a specified key.īoolean replace(K key, V oldValue, V newValue) If the specified key is not already associated with a value or is associated with null, associates it with the given non-null value. V merge(K key, V value, BiFunction remappingFunction) This method returns true if the map is empty returns false if it contains at least one key.

#Method map code#

It returns the hash code value for the Map It returns the value to which the specified key is mapped, or defaultValue if the map contains no mapping for the key. V getOrDefault(Object key, V defaultValue) This method returns the object that contains the value associated with the key. It performs the given action for each entry in the map until all entries have been processed or the action throws an exception. It is used to compare the specified Object with the Map. This method returns true if some key equal to the key exists within the map, else return false. This method returns true if some value equal to the value exists within the map, else return false. It is used to compute a new mapping given the key and its current mapped value if the value for the specified key is present and non-null. V computeIfPresent(K key, BiFunction remappingFunction) It is used to compute its value using the given mapping function, if the specified key is not already associated with a value (or is mapped to null), and enters it into this map unless null. 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.

#Method map update#

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. Now, let's iterate over this map, by going over each Map.Entry in the entrySet(), and extracing the key and value from each of those entries: for (Map.Entry pair : map.A map contains values on the basis of key, i.e.