public abstract class

AbstractMap

extends Object
implements Map<K, V>
java.lang.Object
   ↳ java.util.AbstractMap<K, V>
Known Direct Subclasses
Known Indirect Subclasses

Class Overview

This class is an abstract implementation of the Map interface. This implementation does not support adding. A subclass must implement the abstract method entrySet().

Summary

Protected Constructors
AbstractMap()
Constructs a new instance of this AbstractMap.
Public Methods
void clear()
Removes all elements from this map, leaving it empty.
boolean containsKey(Object key)
Returns whether this map contains the specified key.
boolean containsValue(Object value)
Returns whether this map contains the specified value.
abstract Set<Entry<K, V>> entrySet()
Returns a set containing all of the mappings in this map.
boolean equals(Object object)
Compares the specified object to this instance, and returns true if the specified object is a map and both maps contain the same mappings.
V get(Object key)
Returns the value of the mapping with the specified key.
int hashCode()
Returns the hash code for this object.
boolean isEmpty()
Returns whether this map is empty.
Set<K> keySet()
Returns a set of the keys contained in this map.
V put(K key, V value)
Maps the specified key to the specified value.
void putAll(Map<? extends K, ? extends V> map)
Copies every mapping in the specified map to this map.
V remove(Object key)
Removes a mapping with the specified key from this Map.
int size()
Returns the number of elements in this map.
String toString()
Returns the string representation of this map.
Collection<V> values()
Returns a collection of the values contained in this map.
Protected Methods
Object clone()
Returns a new instance of the same class as this instance, whose slots have been filled in with the values of the slots of this instance.
[Expand]
Inherited Methods
From class java.lang.Object
From interface java.util.Map

Protected Constructors

protected AbstractMap ()

Constructs a new instance of this AbstractMap.

Public Methods

public void clear ()

Removes all elements from this map, leaving it empty.

Throws
UnsupportedOperationException if removing from this map is not supported.
See Also

public boolean containsKey (Object key)

Returns whether this map contains the specified key.

Parameters
key the key to search for.
Returns
  • true if this map contains the specified key, false otherwise.

public boolean containsValue (Object value)

Returns whether this map contains the specified value.

Parameters
value the value to search for.
Returns
  • true if this map contains the specified value, false otherwise.

public abstract Set<Entry<K, V>> entrySet ()

Returns a set containing all of the mappings in this map. Each mapping is an instance of Map.Entry. As the set is backed by this map, changes in one will be reflected in the other.

Returns
  • a set of the mappings.

public boolean equals (Object object)

Compares the specified object to this instance, and returns true if the specified object is a map and both maps contain the same mappings.

Parameters
object the object to compare with this object.
Returns
  • boolean true if the object is the same as this object, and false if it is different from this object.
See Also

public V get (Object key)

Returns the value of the mapping with the specified key.

Parameters
key the key.
Returns
  • the value of the mapping with the specified key, or null if no mapping for the specified key is found.

public int hashCode ()

Returns the hash code for this object. Objects which are equal must return the same value for this method.

Returns
  • the hash code of this object.
See Also

public boolean isEmpty ()

Returns whether this map is empty.

Returns
  • true if this map has no elements, false otherwise.
See Also

public Set<K> keySet ()

Returns a set of the keys contained in this map. The set is backed by this map so changes to one are reflected by the other. The returned set does not support adding.

Returns
  • a set of the keys.

public V put (K key, V value)

Maps the specified key to the specified value.

Parameters
key the key.
value the value.
Returns
  • the value of any previous mapping with the specified key or null if there was no mapping.
Throws
UnsupportedOperationException if adding to this map is not supported.
ClassCastException if the class of the key or value is inappropriate for this map.
IllegalArgumentException if the key or value cannot be added to this map.
NullPointerException if the key or value is null and this Map does not support null keys or values.

public void putAll (Map<? extends K, ? extends V> map)

Copies every mapping in the specified map to this map.

Parameters
map the map to copy mappings from.
Throws
UnsupportedOperationException if adding to this map is not supported.
ClassCastException if the class of a key or value is inappropriate for this map.
IllegalArgumentException if a key or value cannot be added to this map.
NullPointerException if a key or value is null and this map does not support null keys or values.

public V remove (Object key)

Removes a mapping with the specified key from this Map.

Parameters
key the key of the mapping to remove.
Returns
  • the value of the removed mapping or null if no mapping for the specified key was found.
Throws
UnsupportedOperationException if removing from this map is not supported.

public int size ()

Returns the number of elements in this map.

Returns
  • the number of elements in this map.

public String toString ()

Returns the string representation of this map.

Returns
  • the string representation of this map.

public Collection<V> values ()

Returns a collection of the values contained in this map. The collection is backed by this map so changes to one are reflected by the other. The collection supports remove, removeAll, retainAll and clear operations, and it does not support add or addAll operations.

This method returns a collection which is the subclass of AbstractCollection. The iterator method of this subclass returns a "wrapper object" over the iterator of map's entrySet(). The size method wraps the map's size method and the contains method wraps the map's containsValue method.

The collection is created when this method is called for the first time and returned in response to all subsequent calls. This method may return different collections when multiple concurrent calls occur to this method, since no synchronization is performed.

Returns
  • a collection of the values contained in this map.

Protected Methods

protected Object clone ()

Returns a new instance of the same class as this instance, whose slots have been filled in with the values of the slots of this instance.

Returns
  • a shallow copy of this object.
Throws
CloneNotSupportedException if the receiver's class does not implement the interface Cloneable.