java.lang.Object
java.util.AbstractMap<K,V>
java.util.EnumMap<K,V>
public class EnumMap<K extends Enum<K>,V>
A specialized Map implementation for use with enum type keys. All of the keys in an enum map must come from a single enum type that is specified, explicitly or implicitly, when the map is created. Enum maps are represented internally as arrays. This representation is extremely compact and efficient.
Enum maps are maintained in the natural order of their keys (the order in which the enum constants are declared). This is reflected in the iterators returned by the collections views (keySet(), entrySet(), and values()).
Iterators returned by the collection views are weakly consistent: they will never throw ConcurrentModificationException and they may or may not show the effects of any modifications to the map that occur while the iteration is in progress.
Null keys are not permitted. Attempts to insert a null key will throw NullPointerException. Attempts to test for the presence of a null key or to remove one will, however, function properly. Null values are permitted.
Like most collection implementations EnumMap is not synchronized. If multiple threads access an enum map concurrently, and at least one of the threads modifies the map, it should be synchronized externally. This is typically accomplished by synchronizing on some object that naturally encapsulates the enum map. If no such object exists, the map should be "wrapped" using the Collections.synchronizedMap(java.util.Map ) method. This is best done at creation time, to prevent accidental unsynchronized access:
Map<EnumKey, V> m = Collections.synchronizedMap(new EnumMap(...));
Implementation note: All basic operations execute in constant time. They are likely (though not guaranteed) to be faster than their HashMap counterparts.
This class is a member of the Java Collections Framework.
EnumSet, Serialized Form
Map.Entry<K,V> Constructor Summary EnumMap(Class<K> keyType)
EnumMap(EnumMap<K,? extends V> m)
EnumMap(Map<K,? extends V> m)
void clear()
EnumMap<K,V> clone()
boolean containsKey(Object key)
boolean containsValue(Object value)
Set<Map.Entry<K,V>> entrySet()
Set view of the mappings contained in this map. boolean equals(Object o)
V get(Object key)
Set<K> keySet()
Set view of the keys contained in this map. V put(K key, V value)
void putAll(Map<? extends K,? extends V> m)
V remove(Object key)
int size()
Collection<V> values()
Collection view of the values contained in this map. EnumMap
public EnumMap(Class<K> keyType)
keyType - the class object of the key type for this enum map
NullPointerException - if keyType is null
public EnumMap(EnumMap<K,? extends V> m)
m - the enum map from which to initialize this enum map
NullPointerException - if m is null
public EnumMap(Map<K,? extends V> m)
EnumMap(EnumMap). Otherwise, the specified map must contain at least one mapping (in order to determine the new enum map's key type).
m - the map from which to initialize this enum map
IllegalArgumentException - if m is not an EnumMap instance and contains no mappings
NullPointerException - if m is null
public int size()
size in interface Map<K extends Enum<K>,V>
size in class AbstractMap<K extends Enum<K>,V>
public boolean containsValue(Object value)
containsValue in interface Map<K extends Enum<K>,V>
containsValue in class AbstractMap<K extends Enum<K>,V>
value - the value whose presence in this map is to be tested
public boolean containsKey(Object key)
containsKey in interface Map<K extends Enum<K>,V>
containsKey in class AbstractMap<K extends Enum<K>,V>
key - the key whose presence in this map is to be tested
public V get(Object key)
get in interface Map<K extends Enum<K>,V>
get in class AbstractMap<K extends Enum<K>,V>
key - the key whose associated value is to be returned
AbstractMap.containsKey(Object)
public V put(K key,
V value)
put in interface Map<K extends Enum<K>,V>
put in class AbstractMap<K extends Enum<K>,V>
key - the key with which the specified value is to be associated
value - the value to be associated with the specified key
NullPointerException - if the specified key is null
public V remove(Object key)
remove in interface Map<K extends Enum<K>,V>
remove in class AbstractMap<K extends Enum<K>,V>
key - the key whose mapping is to be removed from the map
public void putAll(Map<? extends K,? extends V> m)
putAll in interface Map<K extends Enum<K>,V>
putAll in class AbstractMap<K extends Enum<K>,V>
m - the mappings to be stored in this map
NullPointerException - the specified map is null, or if one or more keys in the specified map are null
public void clear()
clear in interface Map<K extends Enum<K>,V>
clear in class AbstractMap<K extends Enum<K>,V>
public Set<K> keySet()
Set view of the keys contained in this map. The returned set obeys the general contract outlined in Map.keySet(). The set's iterator will return the keys in their natural order (the order in which the enum constants are declared).
keySet in interface Map<K extends Enum<K>,V>
keySet in class AbstractMap<K extends Enum<K>,V>
public Collection<V> values()
Collection view of the values contained in this map. The returned collection obeys the general contract outlined in Map.values(). The collection's iterator will return the values in the order their corresponding keys appear in map, which is their natural order (the order in which the enum constants are declared).
values in interface Map<K extends Enum<K>,V>
values in class AbstractMap<K extends Enum<K>,V>
public Set<Map.Entry<K,V>> entrySet()
Set view of the mappings contained in this map. The returned set obeys the general contract outlined in Map.keySet(). The set's iterator will return the mappings in the order their keys appear in map, which is their natural order (the order in which the enum constants are declared).
entrySet in interface Map<K extends Enum<K>,V>
entrySet in class AbstractMap<K extends Enum<K>,V>
public boolean equals(Object o)
Map.equals(Object) contract.
equals in interface Map<K extends Enum<K>,V>
equals in class AbstractMap<K extends Enum<K>,V>
o - the object to be compared for equality with this map
Object.hashCode(), Hashtable
public EnumMap<K,V> clone()
clone in class AbstractMap<K extends Enum<K>,V>
Cloneable
Copyright © 2004, 2010 Oracle and/or its affiliates. All rights reserved. Use is subject to license terms. Also see the documentation redistribution policy.
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