edu.umd.cloud9.util.map
Class HMapIS

java.lang.Object
  edu.umd.cloud9.util.map.HMapIS

All Implemented Interfaces:

MapIS, Serializable, Cloneable

public class HMapIS
extends Object
implements MapIS, Cloneable, Serializable

Hash-based implementation of the MapIS interface. MapIS is a specialized variant the standard Java Map interface, except that the keys are hard coded as ints and values are hard coded as shorts for efficiency reasons. This implementation was adapted from HashMap version 1.73, 03/13/07. See this benchmark for an efficiency comparison.

See Also:

Serialized Form

Field Summary

Fields inherited from interface edu.umd.cloud9.util.map.MapIS

DEFAULT_VALUE

Constructor Summary

HMapIS()
Constructs an empty HMapIS with the default initial capacity (1024) and the default load factor (0.75).

HMapIS(int initialCapacity)
Constructs an empty HMapIS with the specified initial capacity and the default load factor (0.75).

HMapIS(int initialCapacity, float loadFactor)
Constructs an empty HMapIS with the specified initial capacity and load factor.

HMapIS(MapIS m)
Constructs a new HMapIS with the same mappings as the specified MapIS.

Method Summary

void	clear() Removes all of the mappings from this map.
Object	clone() Returns a shallow copy of this HMapIS instance: the keys and values themselves are not cloned.
boolean	containsKey(int key) Returns true if this map contains a mapping for the specified key.
boolean	containsValue(short value) Returns true if this map contains one or more mappings with the specified value.
int	dot(MapIS m) Computes the dot product of this map with another map.
Set<MapIS.Entry>	entrySet() Returns a Set view of the mappings contained in this map.
short	get(int key) Returns the value to which the specified key is mapped, or throws NoSuchElementException if this map contains no mapping for the key.
MapIS.Entry[]	getEntriesSortedByValue() Returns entries sorted by descending value.
MapIS.Entry[]	getEntriesSortedByValue(int n) Returns top n entries sorted by descending value.
void	increment(int key) Increments the key.
void	increment(int key, short value)
boolean	isEmpty() Returns true if this map contains no key-value mappings.
Set<Integer>	keySet() Returns a Set view of the keys contained in this map.
void	plus(MapIS m) Adds values of keys from another map to this map.
short	put(int key, short value) Associates the specified value with the specified key in this map.
void	putAll(MapIS m) Copies all of the mappings from the specified map to this map.
short	remove(int key) Removes the mapping for a key from this map if it is present.
int	size() Returns the number of key-value mappings in this map.
String	toString()
Collection<Short>	values() Returns a Collection view of the values contained in this map.

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

Methods inherited from interface edu.umd.cloud9.util.map.MapIS

equals, hashCode

Constructor Detail

HMapIS

public HMapIS(int initialCapacity,
              float loadFactor)

Constructs an empty HMapIS with the specified initial capacity and load factor.

Parameters:

initialCapacity - the initial capacity

loadFactor - the load factor

Throws:

IllegalArgumentException - if the initial capacity is negative or the load factor is nonpositive

HMapIS

public HMapIS(int initialCapacity)

Constructs an empty HMapIS with the specified initial capacity and the default load factor (0.75).

Parameters:

initialCapacity - the initial capacity.

Throws:

IllegalArgumentException - if the initial capacity is negative.

HMapIS

public HMapIS()

Constructs an empty HMapIS with the default initial capacity (1024) and the default load factor (0.75).

HMapIS

public HMapIS(MapIS m)

Constructs a new HMapIS with the same mappings as the specified MapIS. The HMapIS is created with default load factor (0.75) and an initial capacity sufficient to hold the mappings in the specified MapIS.

Parameters:

m - the map whose mappings are to be placed in this map

Throws:

NullPointerException - if the specified map is null

Method Detail

size

public int size()

Description copied from interface: MapIS

Returns the number of key-value mappings in this map.

Specified by:

size in interface MapIS

Returns:

the number of key-value mappings in this map

isEmpty

public boolean isEmpty()

Description copied from interface: MapIS

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

Specified by:

isEmpty in interface MapIS

Returns:

true if this map contains no key-value mappings

get

public short get(int key)

Description copied from interface: MapIS

Returns the value to which the specified key is mapped, or throws NoSuchElementException if this map contains no mapping for the key.

Specified by:

get in interface MapIS

Parameters:

key - the key whose associated value is to be returned

Returns:

the value to which the specified key is mapped

containsKey

public boolean containsKey(int key)

Description copied from interface: MapIS

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

Specified by:

containsKey in interface MapIS

Parameters:

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

Returns:

true if this map contains a mapping for the specified key

put

public short put(int key,
                 short value)

Description copied from interface: MapIS

Associates the specified value with the specified key in this map. If the map previously contained a mapping for the key, the old value is replaced by the specified value.

Specified by:

put in interface MapIS

Parameters:

key - key with which the specified value is to be associated

value - value to be associated with the specified key

putAll

public void putAll(MapIS m)

Description copied from interface: MapIS

Copies all of the mappings from the specified map to this map.

Specified by:

putAll in interface MapIS

Parameters:

m - mappings to be stored in this map

remove

public short remove(int key)

Description copied from interface: MapIS

Removes the mapping for a key from this map if it is present. No action is performed if this map does not contain the key.

Specified by:

remove in interface MapIS

Parameters:

key - key whose mapping is to be removed from the map

clear

public void clear()

Description copied from interface: MapIS

Removes all of the mappings from this map. The map will be empty after this call returns.

Specified by:

clear in interface MapIS

containsValue

public boolean containsValue(short value)

Description copied from interface: MapIS

Returns true if this map contains one or more mappings with the specified value.

Specified by:

containsValue in interface MapIS

Parameters:

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

Returns:

true this map contains one or more mappings with the specified value

clone

public Object clone()

Returns a shallow copy of this HMapIS instance: the keys and values themselves are not cloned.

Overrides:

clone in class Object

Returns:

a shallow copy of this map

keySet

public Set<Integer> keySet()

Description copied from interface: MapIS

Returns a Set view of the keys contained in this map. Note that this is a inefficient operation since it triggers autoboxing of the int keys, which is exactly what this implementation is trying to avoid. Unlike a standard Java Map, values in the backing map cannot be altered with this collection view.

Specified by:

keySet in interface MapIS

Returns:

a set view of the keys contained in this map

values

public Collection<Short> values()

Description copied from interface: MapIS

Returns a Collection view of the values contained in this map. Note that this is a inefficient operation since it triggers autoboxing of the int values, which is exactly what this implementation is trying to avoid. Unlike a standard Java Map, values in the backing map cannot be altered with this collection view.

Specified by:

values in interface MapIS

Returns:

a collection view of the values contained in this map

entrySet

public Set<MapIS.Entry> entrySet()

Description copied from interface: MapIS

Returns a Set view of the mappings contained in this map. The set is backed by the map, so changes to the map are reflected in the set, and vice-versa. See Map.entrySet() for more details.

Specified by:

entrySet in interface MapIS

Returns:

a set view of the mappings contained in this map

toString

public String toString()

Overrides:

toString in class Object

plus

public void plus(MapIS m)

Adds values of keys from another map to this map.

Parameters:

m - the other map

dot

public int dot(MapIS m)

Computes the dot product of this map with another map.

Parameters:

m - the other map

increment

public void increment(int key)

Increments the key. If the key does not exist in the map, its value is set to one.

Parameters:

key - key to increment

increment

public void increment(int key,
                      short value)

getEntriesSortedByValue

public MapIS.Entry[] getEntriesSortedByValue()

Returns entries sorted by descending value. Ties broken by the key.

Returns:

entries sorted by descending value

getEntriesSortedByValue

public MapIS.Entry[] getEntriesSortedByValue(int n)

Returns top n entries sorted by descending value. Ties broken by the key.

Parameters:

n - number of entries to return

Returns:

top n entries sorted by descending value