File	Doc	Category	Size	Date	Package
EnumMap.java	API Doc	Java SE 6 API	23809	Tue Jun 10 00:25:52 BST 2008	java.util

EnumMap

• java.lang.Object
  • java.util.AbstractMap

Map<EnumKey, V> m
= Collections.synchronizedMap(new EnumMap<EnumKey, V>(...));

Fields Summary
private final Class	keyType The Class object for the enum type of all the keys of this map.
private transient K[]	keyUniverse All of the values comprising K. (Cached for performance.)
private transient Object[]	vals Array representation of this map. The ith element is the value to which universe[i] is currently mapped, or null if it isn't mapped to anything, or NULL if it's mapped to null.
private transient int	size The number of mappings in this map.
private static final Object	NULL Distinguished non-null value for representing null values.
private static Enum[]	ZERO_LENGTH_ENUM_ARRAY
private transient Set	entrySet This field is initialized to contain an instance of the entry set view the first time this view is requested. The view is stateless, so there's no reason to create more than one.
private static final long	serialVersionUID

Constructors Summary
public EnumMap(Class keyType) Creates an empty enum map with the specified key type. param keyType the class object of the key type for this enum map throws NullPointerException if keyType is null this.keyType = keyType; keyUniverse = getKeyUniverse(keyType); vals = new Object[keyUniverse.length];
public EnumMap(EnumMap m) Creates an enum map with the same key type as the specified enum map, initially containing the same mappings (if any). param m the enum map from which to initialize this enum map throws NullPointerException if m is null keyType = m.keyType; keyUniverse = m.keyUniverse; vals = (Object[]) m.vals.clone(); size = m.size;
public EnumMap(Map m) Creates an enum map initialized from the specified map. If the specified map is an EnumMap instance, this constructor behaves identically to {@link #EnumMap(EnumMap)}. Otherwise, the specified map must contain at least one mapping (in order to determine the new enum map's key type). param m the map from which to initialize this enum map throws IllegalArgumentException if m is not an EnumMap instance and contains no mappings throws NullPointerException if m is null if (m instanceof EnumMap) { EnumMap<K, ? extends V> em = (EnumMap<K, ? extends V>) m; keyType = em.keyType; keyUniverse = em.keyUniverse; vals = (Object[]) em.vals.clone(); size = em.size; } else { if (m.isEmpty()) throw new IllegalArgumentException("Specified map is empty"); keyType = m.keySet().iterator().next().getDeclaringClass(); keyUniverse = getKeyUniverse(keyType); vals = new Object[keyUniverse.length]; putAll(m); }

Methods Summary
public void	clear() Removes all mappings from this map. Arrays.fill(vals, null); size = 0;
public java.util.EnumMap	clone() Returns a shallow copy of this enum map. (The values themselves are not cloned. return a shallow copy of this enum map EnumMap<K, V> result = null; try { result = (EnumMap<K, V>) super.clone(); } catch(CloneNotSupportedException e) { throw new AssertionError(); } result.vals = (Object[]) result.vals.clone(); return result;
public boolean	containsKey(java.lang.Object key) Returns true if this map contains a mapping for the specified key. param key the key whose presence in this map is to be tested return true if this map contains a mapping for the specified key return isValidKey(key) && vals[((Enum)key).ordinal()] != null;
private boolean	containsMapping(java.lang.Object key, java.lang.Object value) return isValidKey(key) && maskNull(value).equals(vals[((Enum)key).ordinal()]);
public boolean	containsValue(java.lang.Object value) Returns true if this map maps one or more keys to the specified value. param value the value whose presence in this map is to be tested return true if this map maps one or more keys to this value value = maskNull(value); for (Object val : vals) if (value.equals(val)) return true; return false;
public java.util.Set	entrySet() Returns a {@link Set} view of the mappings contained in this map. The returned set obeys the general contract outlined in {@link 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). return a set view of the mappings contained in this enum map Set<Map.Entry<K,V>> es = entrySet; if (es != null) return es; else return entrySet = new EntrySet();
public boolean	equals(java.lang.Object o) Compares the specified object with this map for equality. Returns true if the given object is also a map and the two maps represent the same mappings, as specified in the {@link Map#equals(Object)} contract. param o the object to be compared for equality with this map return true if the specified object is equal to this map if (!(o instanceof EnumMap)) return super.equals(o); EnumMap em = (EnumMap)o; if (em.keyType != keyType) return size == 0 && em.size == 0; // Key types match, compare each value for (int i = 0; i < keyUniverse.length; i++) { Object ourValue = vals[i]; Object hisValue = em.vals[i]; if (hisValue != ourValue && (hisValue == null || !hisValue.equals(ourValue))) return false; } return true;
public V	get(java.lang.Object key) Returns the value to which the specified key is mapped, or {@code null} if this map contains no mapping for the key. More formally, if this map contains a mapping from a key {@code k} to a value {@code v} such that {@code (key == k)}, then this method returns {@code v}; otherwise it returns {@code null}. (There can be at most one such mapping.) A return value of {@code null} does not necessarily indicate that the map contains no mapping for the key; it's also possible that the map explicitly maps the key to {@code null}. The {@link #containsKey containsKey} operation may be used to distinguish these two cases. return (isValidKey(key) ? unmaskNull(vals[((Enum)key).ordinal()]) : null);
private static K[]	getKeyUniverse(java.lang.Class keyType) Returns all of the values comprising K. The result is uncloned, cached, and shared by all callers. return SharedSecrets.getJavaLangAccess() .getEnumConstantsShared(keyType);
private boolean	isValidKey(java.lang.Object key) Returns true if key is of the proper type to be a key in this enum map. if (key == null) return false; // Cheaper than instanceof Enum followed by getDeclaringClass Class keyClass = key.getClass(); return keyClass == keyType || keyClass.getSuperclass() == keyType;
public java.util.Set	keySet() Returns a {@link Set} view of the keys contained in this map. The returned set obeys the general contract outlined in {@link Map#keySet()}. The set's iterator will return the keys in their natural order (the order in which the enum constants are declared). return a set view of the keys contained in this enum map Set<K> ks = keySet; if (ks != null) return ks; else return keySet = new KeySet();
private java.lang.Object	maskNull(java.lang.Object value) return (value == null ? NULL : value);
public V	put(K key, V value) Associates the specified value with the specified key in this map. If the map previously contained a mapping for this key, the old value is replaced. param key the key with which the specified value is to be associated param value the value to be associated with the specified key return the previous value associated with specified key, or null if there was no mapping for key. (A null return can also indicate that the map previously associated null with the specified key.) throws NullPointerException if the specified key is null typeCheck(key); int index = ((Enum)key).ordinal(); Object oldValue = vals[index]; vals[index] = maskNull(value); if (oldValue == null) size++; return unmaskNull(oldValue);
public void	putAll(java.util.Map m) Copies all of the mappings from the specified map to this map. These mappings will replace any mappings that this map had for any of the keys currently in the specified map. param m the mappings to be stored in this map throws NullPointerException the specified map is null, or if one or more keys in the specified map are null if (m instanceof EnumMap) { EnumMap<? extends K, ? extends V> em = (EnumMap<? extends K, ? extends V>)m; if (em.keyType != keyType) { if (em.isEmpty()) return; throw new ClassCastException(em.keyType + " != " + keyType); } for (int i = 0; i < keyUniverse.length; i++) { Object emValue = em.vals[i]; if (emValue != null) { if (vals[i] == null) size++; vals[i] = emValue; } } } else { super.putAll(m); }
private void	readObject(java.io.ObjectInputStream s) Reconstitute the EnumMap instance from a stream (i.e., deserialize it). // Read in the key type and any hidden stuff s.defaultReadObject(); keyUniverse = getKeyUniverse(keyType); vals = new Object[keyUniverse.length]; // Read in size (number of Mappings) int size = s.readInt(); // Read the keys and values, and put the mappings in the HashMap for (int i = 0; i < size; i++) { K key = (K) s.readObject(); V value = (V) s.readObject(); put(key, value); }
public V	remove(java.lang.Object key) Removes the mapping for this key from this map if present. param key the key whose mapping is to be removed from the map return the previous value associated with specified key, or null if there was no entry for key. (A null return can also indicate that the map previously associated null with the specified key.) if (!isValidKey(key)) return null; int index = ((Enum)key).ordinal(); Object oldValue = vals[index]; vals[index] = null; if (oldValue != null) size--; return unmaskNull(oldValue);
private boolean	removeMapping(java.lang.Object key, java.lang.Object value) if (!isValidKey(key)) return false; int index = ((Enum)key).ordinal(); if (maskNull(value).equals(vals[index])) { vals[index] = null; size--; return true; } return false;
public int	size() Returns the number of key-value mappings in this map. return the number of key-value mappings in this map return size;
private void	typeCheck(K key) Throws an exception if e is not of the correct type for this enum set. Class keyClass = key.getClass(); if (keyClass != keyType && keyClass.getSuperclass() != keyType) throw new ClassCastException(keyClass + " != " + keyType);
private V	unmaskNull(java.lang.Object value) return (V) (value == NULL ? null : value);
public java.util.Collection	values() Returns a {@link Collection} view of the values contained in this map. The returned collection obeys the general contract outlined in {@link 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). return a collection view of the values contained in this map Collection<V> vs = values; if (vs != null) return vs; else return values = new Values();
private void	writeObject(java.io.ObjectOutputStream s) Save the state of the EnumMap instance to a stream (i.e., serialize it). serialData The size of the enum map (the number of key-value mappings) is emitted (int), followed by the key (Object) and value (Object) for each key-value mapping represented by the enum map. // Write out the key type and any hidden stuff s.defaultWriteObject(); // Write out size (number of Mappings) s.writeInt(size); // Write out keys and values (alternating) for (Map.Entry<K,V> e : entrySet()) { s.writeObject(e.getKey()); s.writeObject(e.getValue()); }