Java HashMap Methods

Method 

Description

Return Type

clear()

Remove all entries from the map.

void

clone()

Make a copy of the HashMap.

Object

compute()

Calculate a value for an entry using its key and the current value (if it exists).

V

computeIfAbsent()

Calculate a value for an entry based on its key only if an entry with that key does not already exist.

V

computeIfPresent()

Calculate a new value for an entry using its key and current value, but perform this operation only if an entry with the given key already exists.

V

containsKey()

Determine whether an entry with the specified key exists in the map.

boolean

containsValue()

Determine if an entry with the specified value exists in the map.

boolean

entrySet()

Provide a set containing all entries in the map.

Set< Map.Entry<K,V> >

forEach()

Execute an action for each entry in the map.

void

get()

Retrieve the value associated with the specified key.

V

getOrDefault()

Retrieve the value associated with the specified key, or return a default value if the entry is not found.

V

isEmpty()

Determine if the map is empty.

boolean

keyset()

Provide a set containing all keys in the map.

Set<K>

merge()

Calculate a value for an entry using its key and value, or assign a specific value if the entry does not yet exist.

V

put()

Add an entry to the map.

V

putAll()

Copy all entries from another map into this one.

void

putIfAbsent()

Add an entry to the map, but do so only if an entry with the same key does not already exist.

V

remove()

Delete an entry from the map.

V|boolean

replace()

Update an entry in the map only if it exists.

V|boolean

replaceAll()

Replace the value of each entry with the result of an operation.

void

size()

Provide the count of entries in the map.

int

values()

Provide a collection containing all of the values in the map.

Collection<V>