java.util
Interface Map

All Known Implementing Classes:

AbstractMap, HashMap, Hashtable

public interface Map

Map has a set of keys, each key is mapped to a single value.

Nested Class Summary

static interface

Map.Entry Map.Entry is a key/value mapping which is contained in a Map.

Method Summary

void	clear() Removes all elements from this Map, leaving it empty.
boolean	containsKey(java.lang.Object key) Searches this Map for the specified key.
boolean	containsValue(java.lang.Object value) Searches this Map for the specified value.
Set	entrySet() Returns a Set whose elements comprise all of the mappings that are to be found in this Map.
boolean	equals(java.lang.Object object) Compares the argument to the receiver, and answers true if they represent the same object using a class specific comparison.
java.lang.Object	get(java.lang.Object key) Answers the value of the mapping with the specified key.
int	hashCode() Answers an integer hash code for the receiver.
boolean	isEmpty() Answers if this Map has no elements, a size of zero.
Set	keySet() Answers a Set of the keys contained in this Map.
java.lang.Object	put(java.lang.Object key, java.lang.Object value) Maps the specified key to the specified value.
void	putAll(Map map) Copies every mapping in the specified Map to this Map.
java.lang.Object	remove(java.lang.Object key) Removes a mapping with the specified key from this Map.
int	size() Answers the number of elements in this Map.
Collection	values() Returns all of the current Map values in a Collection.

Method Detail

clear

public void clear()

Removes all elements from this Map, leaving it empty.

Throws:

UnsupportedOperationException - when removing from this Map is not supported

See Also:

isEmpty(), size()

containsKey

public boolean containsKey(java.lang.Object key)

Searches this Map for the specified key.

Parameters:

key - the object to search for

Returns:

true if key is a key of this Map, false otherwise

containsValue

public boolean containsValue(java.lang.Object value)

Searches this Map for the specified value.

Parameters:

value - the object to search for

Returns:

true if value is a value of this Map, false otherwise

entrySet

public Set entrySet()

Returns a Set whose elements comprise all of the mappings that are to be found in this Map. Information on each of the mappings is encapsulated in a separate Map.Entry instance. As the Set is backed by this Map, users should be aware that changes in one will be immediately visible in the other.

Returns:

a Set of the mappings

equals

public boolean equals(java.lang.Object object)

Compares the argument to the receiver, and answers true if they represent the same object using a class specific comparison.

Parameters:

object - Object the object to compare with this object.

Returns:

boolean true if the object is the same as this object false if it is different from this object.

See Also:

hashCode()

get

public java.lang.Object get(java.lang.Object key)

Answers the value of the mapping with the specified key.

Parameters:

key - the key

Returns:

the value of the mapping with the specified key

hashCode

public int hashCode()

Answers an integer hash code for the receiver. Objects which are equal answer the same value for this method.

Returns:

the receiver's hash

See Also:

equals(java.lang.Object)

isEmpty

public boolean isEmpty()

Answers if this Map has no elements, a size of zero.

Returns:

true if this Map has no elements, false otherwise

See Also:

size()

keySet

public Set keySet()

Answers a Set of the keys contained in this Map. The set is backed by this Map so changes to one are relected by the other. The set does not support adding.

Returns:

a Set of the keys

put

public java.lang.Object put(java.lang.Object key,
                            java.lang.Object 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 - when adding to this Map is not supported

ClassCastException - when the class of the key or value is inappropriate for this Map

IllegalArgumentException - when the key or value cannot be added to this Map

NullPointerException - when the key or value is null and this Map does not support null keys or values

putAll

public void putAll(Map map)

Copies every mapping in the specified Map to this Map.

Parameters:

map - the Map to copy mappings from

Throws:

UnsupportedOperationException - when adding to this Map is not supported

ClassCastException - when the class of a key or value is inappropriate for this Map

IllegalArgumentException - when a key or value cannot be added to this Map

NullPointerException - when a key or value is null and this Map does not support null keys or values

remove

public java.lang.Object remove(java.lang.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 key is not a key in this Map

Throws:

UnsupportedOperationException - when removing from this Map is not supported

size

public int size()

Answers the number of elements in this Map.

Returns:

the number of elements in this Map

values

public Collection values()

Returns all of the current Map values in a Collection. As the returned Collection is backed by this Map, users should be aware that changes in one will be immediately visible in the other.

Returns:

a Collection of the values