com.hp.hpl.jena.util
Class OneToManyMap<From,To>

java.lang.Object
  com.hp.hpl.jena.util.OneToManyMap<From,To>

All Implemented Interfaces:

Map<From,To>

public class OneToManyMap<From,To>
extends Object
implements Map<From,To>

An extension to a standard map that supports one-to-many mappings: that is, there may be zero, one or many values corresponding to a given key.

Version:

CVS info: $Id: OneToManyMap.java,v 1.2 2009-08-08 11:25:18 andy_seaborne Exp $

Author:

Ian Dickinson, HP Labs (email)

Nested Class Summary

static class

OneToManyMap.Entry<From,To> Helper class to implement the Map.Entry interface to enumerate entries in the map

Constructor Summary

OneToManyMap()
Construct a new empty one-to-many map

OneToManyMap(OneToManyMap<From,To> map)
Construct a new one-to-many map whose contents are initialised from the existing map.

Method Summary

void	clear() Clear all entries from the map.
boolean	contains(Object key, Object value) Answer true if this mapping contains the pair (key, value).
boolean	containsKey(Object key) Answer true if the map contains the given value as a key.
boolean	containsValue(Object value) Answer true if the map contains the given object as a value stored against any key.
Set<Map.Entry<From,To>>	entrySet() Answer a set of the mappings in this map.
boolean	equals(Object o) Compares the specified object with this map for equality.
To	get(Object key) Get a value for this key.
Iterator<To>	getAll(Object key) Answer an iterator over all of the values for the given key.
int	hashCode() Returns the hash code value for this map.
boolean	isEmpty() Answer true if the map is empty of key-value mappings.
Set<From>	keySet() Answer a set of the keys in this map
To	put(From key, To value) Associates the given value with the given key.
void	putAll(Map<? extends From,? extends To> m) Put all entries from one map into this map.
To	remove(Object key) Remove all of the associations for the given key.
void	remove(Object key, Object value) Remove the specific association between the given key and value.
int	size() Answer the number of key-value mappings in the map
String	toString() Answer a string representation of this map.
Collection<To>	values() Returns a collection view of the values contained in this map.

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

OneToManyMap

public OneToManyMap()

Construct a new empty one-to-many map

OneToManyMap

public OneToManyMap(OneToManyMap<From,To> map)

Construct a new one-to-many map whose contents are initialised from the existing map.

Parameters:

map - An existing one-to-many map

Method Detail

clear

public void clear()

Clear all entries from the map.

Specified by:

clear in interface Map<From,To>

containsKey

public boolean containsKey(Object key)

Answer true if the map contains the given value as a key.

Specified by:

containsKey in interface Map<From,To>

Parameters:

key - The key object to test for

Returns:

True or false

containsValue

public boolean containsValue(Object value)

Answer true if the map contains the given object as a value stored against any key. Note that this is quite an expensive operation in the current implementation.

Specified by:

containsValue in interface Map<From,To>

Parameters:

value - The value to test for

Returns:

True if the value is in the map

contains

public boolean contains(Object key,
                        Object value)

Answer true if this mapping contains the pair (key, value).

Parameters:

key - A key object

value - A value object

Returns:

True if key has value as one of its values in this mapping

entrySet

public Set<Map.Entry<From,To>> entrySet()

Answer a set of the mappings in this map. Each member of the set will be a Map.Entry value.

Specified by:

entrySet in interface Map<From,To>

Returns:

A Set of the mappings as Map.Entry values.

equals

public boolean equals(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. More formally, two maps t1 and t2 represent the same mappings if t1.entrySet().equals(t2.entrySet()). This ensures that the equals method works properly across different implementations of the Map interface.

Specified by:

equals in interface Map<From,To>

Overrides:

equals in class Object

Parameters:

o - The object to be compared for equality with this map.

Returns:

True if the specified object is equal to this map.

get

public To get(Object key)

Get a value for this key. Since this map is explicitly designed to allow there to be more than one mapping per key, this method will return an undetermined instance of the mapping. If no mapping exists, or the selected value is null, null is returned.

Specified by:

get in interface Map<From,To>

Parameters:

key - The key to access the map.

Returns:

One of the values this key corresponds to, or null.

See Also:

getAll(java.lang.Object)

getAll

public Iterator<To> getAll(Object key)

Answer an iterator over all of the values for the given key. An iterator is always supplied, even if the key is not present.

Parameters:

key - The key object

Returns:

An iterator over all of the values for this key in the map

hashCode

public int hashCode()

Returns the hash code value for this map. The hash code of a map is defined to be the sum of the hashCodes of each entry in the map's entrySet view. This ensures that t1.equals(t2) implies that t1.hashCode()==t2.hashCode() for any two maps t1 and t2, as required by the general contract of Object.hashCode

Specified by:

hashCode in interface Map<From,To>

Overrides:

hashCode in class Object

isEmpty

public boolean isEmpty()

Answer true if the map is empty of key-value mappings.

Specified by:

isEmpty in interface Map<From,To>

Returns:

True if there are no entries.

keySet

public Set<From> keySet()

Answer a set of the keys in this map

Specified by:

keySet in interface Map<From,To>

Returns:

The keys of the map as a Set

put

public To put(From key,
              To value)

Associates the given value with the given key. Since this map formulation allows many values for one key, previous associations with the key are not lost. Consequently, the method always returns null (since the replaced value is not defined).

Specified by:

put in interface Map<From,To>

Parameters:

key - The key object

value - The value object

Returns:

Null.

putAll

public void putAll(Map<? extends From,? extends To> m)

Put all entries from one map into this map. Tests for m being a OneToManyMap, and, if so, copies all of the entries for each key.

Specified by:

putAll in interface Map<From,To>

Parameters:

m - The map whose contents are to be copied into this map

remove

public To remove(Object key)

Remove all of the associations for the given key. If only a specific association is to be removed, use remove( java.lang.Object, java.lang.Object ) instead. Has no effect if the key is not present in the map. Since no single specific association with the key is defined, this method always returns null.

Specified by:

remove in interface Map<From,To>

Parameters:

key - All associations with this key will be removed

Returns:

null

remove

public void remove(Object key,
                   Object value)

Remove the specific association between the given key and value. Has no effect if the association is not present in the map. If all values for a particular key have been removed post removing this particular association, the key will no longer appear as a key in the map.

Parameters:

key - The key object

value - The value object

size

public int size()

Answer the number of key-value mappings in the map

Specified by:

size in interface Map<From,To>

Returns:

The number of key-value pairs.

values

public Collection<To> values()

Returns a collection view of the values contained in this map. Specifically, this will be a set, so duplicate values that appear for multiple keys are suppressed.

Specified by:

values in interface Map<From,To>

Returns:

A set of the values contained in this map.

toString

public String toString()

Answer a string representation of this map. This can be quite a long string for large maps.

Overrides:

toString in class Object