java.util
Class Collections.SingletonMap

java.lang.Object
  java.util.AbstractMap
      java.util.Collections.SingletonMap

All Implemented Interfaces:

Map, Serializable

Enclosing class:

Collections

private static class Collections.SingletonMap

extends AbstractMap

implements Serializable

Nested Class Summary

private static class

Collections.SingletonMap.ImmutableEntry

Nested classes inherited from class java.util.AbstractMap

AbstractMap.SimpleEntry

Nested classes inherited from class java.util.Map

Map.Entry

Field Summary

private Set	entrySet
private Object	k
private Set	keySet
private Object	v
private Collection	values

Constructor Summary

(package private)

Collections.SingletonMap(Object key, Object value)

Method Summary

boolean	containsKey(Object key) Returns true if this map contains a mapping for the specified key.
boolean	containsValue(Object value) Returns true if this map maps one or more keys to this value.
Set	entrySet() Returns a set view of the mappings contained in this map.
Object	get(Object key) Returns the value to which this map maps the specified key.
boolean	isEmpty() Returns true if this map contains no key-value mappings.
Set	keySet() Returns a Set view of the keys contained in this map.
int	size() Returns the number of key-value mappings in this map.
Collection	values() Returns a collection view of the values contained in this map.

Methods inherited from class java.util.AbstractMap

clear, clone, equals, hashCode, put, putAll, remove, toString

Methods inherited from class java.lang.Object

finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

k

private final Object k

v

private final Object v

keySet

private transient Set keySet

entrySet

private transient Set entrySet

values

private transient Collection values

Constructor Detail

Collections.SingletonMap

Collections.SingletonMap(Object key,
                         Object value)

Method Detail

size

public int size()

Description copied from class: AbstractMap

Returns the number of key-value mappings in this map. If the map contains more than Integer.MAX_VALUE elements, returns Integer.MAX_VALUE.

This implementation returns entrySet().size().

Specified by:

size in interface Map

Overrides:

size in class AbstractMap

Returns:

the number of key-value mappings in this map.

isEmpty

public boolean isEmpty()

Description copied from class: AbstractMap

Returns true if this map contains no key-value mappings.

This implementation returns size() == 0.

Specified by:

isEmpty in interface Map

Overrides:

isEmpty in class AbstractMap

Returns:

true if this map contains no key-value mappings.

containsKey

public boolean containsKey(Object key)

Description copied from class: AbstractMap

Returns true if this map contains a mapping for the specified key.

This implementation iterates over entrySet() searching for an entry with the specified key. If such an entry is found, true is returned. If the iteration terminates without finding such an entry, false is returned. Note that this implementation requires linear time in the size of the map; many implementations will override this method.

Specified by:

containsKey in interface Map

Overrides:

containsKey in class AbstractMap

Parameters:

key - key whose presence in this map is to be tested.

Returns:

true if this map contains a mapping for the specified key.

containsValue

public boolean containsValue(Object value)

Description copied from class: AbstractMap

Returns true if this map maps one or more keys to this value. More formally, returns true if and only if this map contains at least one mapping to a value v such that (value==null ? v==null : value.equals(v)). This operation will probably require time linear in the map size for most implementations of map.

This implementation iterates over entrySet() searching for an entry with the specified value. If such an entry is found, true is returned. If the iteration terminates without finding such an entry, false is returned. Note that this implementation requires linear time in the size of the map.

Specified by:

containsValue in interface Map

Overrides:

containsValue in class AbstractMap

Parameters:

value - value whose presence in this map is to be tested.

Returns:

true if this map maps one or more keys to this value.

get

public Object get(Object key)

Description copied from class: AbstractMap

Returns the value to which this map maps the specified key. Returns null if the map contains no mapping for this key. A return value of 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 null. The containsKey operation may be used to distinguish these two cases.

This implementation iterates over entrySet() searching for an entry with the specified key. If such an entry is found, the entry's value is returned. If the iteration terminates without finding such an entry, null is returned. Note that this implementation requires linear time in the size of the map; many implementations will override this method.

Specified by:

get in interface Map

Overrides:

get in class AbstractMap

Parameters:

key - key whose associated value is to be returned.

Returns:

the value to which this map maps the specified key.

See Also:

AbstractMap.containsKey(Object)

keySet

public Set keySet()

Description copied from class: AbstractMap

Returns a Set view of the keys contained in this map. The Set is backed by the map, so changes to the map are reflected in the Set, and vice-versa. (If the map is modified while an iteration over the Set is in progress, the results of the iteration are undefined.) The Set supports element removal, which removes the corresponding entry from the map, via the Iterator.remove, Set.remove, removeAll retainAll, and clear operations. It does not support the add or addAll operations.

This implementation returns a Set that subclasses AbstractSet. The subclass's iterator method returns a "wrapper object" over this map's entrySet() iterator. The size method delegates to this map's size method and the contains method delegates to this map's containsKey method.

The Set is created the first time this method is called, and returned in response to all subsequent calls. No synchronization is performed, so there is a slight chance that multiple calls to this method will not all return the same Set.

Specified by:

keySet in interface Map

Overrides:

keySet in class AbstractMap

Returns:

a Set view of the keys contained in this map.

entrySet

public Set entrySet()

Description copied from class: AbstractMap

Returns a set view of the mappings contained in this map. Each element in this set is a Map.Entry. The set is backed by the map, so changes to the map are reflected in the set, and vice-versa. (If the map is modified while an iteration over the set is in progress, the results of the iteration are undefined.) The set supports element removal, which removes the corresponding entry from the map, via the Iterator.remove, Set.remove, removeAll, retainAll and clear operations. It does not support the add or addAll operations.

Specified by:

entrySet in interface Map

Specified by:

entrySet in class AbstractMap

Returns:

a set view of the mappings contained in this map.

values

public Collection values()

Description copied from class: AbstractMap

Returns a collection view of the values contained in this map. The collection is backed by the map, so changes to the map are reflected in the collection, and vice-versa. (If the map is modified while an iteration over the collection is in progress, the results of the iteration are undefined.) The collection supports element removal, which removes the corresponding entry from the map, via the Iterator.remove, Collection.remove, removeAll, retainAll and clear operations. It does not support the add or addAll operations.

This implementation returns a collection that subclasses abstract collection. The subclass's iterator method returns a "wrapper object" over this map's entrySet() iterator. The size method delegates to this map's size method and the contains method delegates to this map's containsValue method.

The collection is created the first time this method is called, and returned in response to all subsequent calls. No synchronization is performed, so there is a slight chance that multiple calls to this method will not all return the same Collection.

Specified by:

values in interface Map

Overrides:

values in class AbstractMap

Returns:

a collection view of the values contained in this map.