Map interface methods (java)

Here are some of the most useful Map methods. m is a Map, b is a boolean, i is an int, set is a Set, col is a Collection, key is an Object used as the key used to store a value, val is an Object stored as the value associated with the key.

Result	Method	Description
Adding key-value pairs to a map
obj =	m.put(key, val)	Creates mapping from key to val. It returns the previous value (or null) associated with the key.
	m.putAll(map2)	Adds all key-value entries from another map, map2.
Removing key-value pairs from a map
	m.clear()	Removes all elements from a Map
obj =	m.remove(key)	Deletes mapping from key to anything. Returns previous value (or null) associated with the key.
Retrieving information from the map
b =	m.containsKey(key)	Returns true if m contains a key key
b =	m.containsValue(val)	Returns true if m contains val as one of the values
obj =	m.get(key)	Returns value corresponding to key, or null if there is no mapping. If null has been stored as a value, use containsKey to see if there is a mapping.
b =	m.isEmpty()	Returns true if m contains no mappings.
i =	m.size()	Returns number of mappings in m.
Retrieving all keys, values, or key-value pairs (necessary for iteration)
set =	m.entrySet()	Returns set of Map.Entry values for all mappings.
set =	m.keySet()	Returns Set of keys.
col =	m.values()	Returns a Collection view of the values in m.