Mega Code Archive
HashNMap stores multiple values by a single key value Values can be retrieved using a direct query or by creating an enumerati
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/*
* JCommon : a free general purpose class library for the Java(tm) platform
*
*
* (C) Copyright 2000-2005, by Object Refinery Limited and Contributors.
*
* Project Info: http://www.jfree.org/jcommon/index.html
*
* This library is free software; you can redistribute it and/or modify it
* under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation; either version 2.1 of the License, or
* (at your option) any later version.
*
* This library is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
* License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
* USA.
*
* [Java is a trademark or registered trademark of Sun Microsystems, Inc.
* in the United States and other countries.]
*
* -------------
* HashNMap.java
* -------------
* (C)opyright 2002-2005, by Thomas Morgner and Contributors.
*
* Original Author: Thomas Morgner;
* Contributor(s): David Gilbert (for Object Refinery Limited);
*
* $Id: HashNMap.java,v 1.7 2005/10/18 13:24:19 mungady Exp $
*
* Changes
* -------
* 20-May-2002 : Initial version
* 10-Dec-2002 : Minor Javadoc updates (DG);
* 29-Jul-2004 : Replaced 'enum' variable name (reserved word in JDK 1.5) (DG);
* 12-Mar-2005 : Some performance improvements, this implementation is no
* longer forced to use ArrayLists, add/put behaviour changed to
* fit the common behaviour of collections.
*
*/
import java.io.Serializable;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.NoSuchElementException;
import java.util.Set;
/**
* The HashNMap can be used to store multiple values by a single key value. The
* values stored can be retrieved using a direct query or by creating an
* enumeration over the stored elements.
*
* @author Thomas Morgner
*/
public class HashNMap implements Serializable, Cloneable {
/** Serialization support. */
private static final long serialVersionUID = -670924844536074826L;
/**
* An helper class to implement an empty iterator. This iterator will always
* return false when <code>hasNext</code> is called.
*/
private static final class EmptyIterator implements Iterator {
/**
* DefaultConstructor.
*/
private EmptyIterator() {
super();
}
/**
* Returns <tt>true</tt> if the iteration has more elements. (In other
* words, returns <tt>true</tt> if <tt>next</tt> would return an element
* rather than throwing an exception.)
*
* @return <tt>true</tt> if the iterator has more elements.
*/
public boolean hasNext() {
return false;
}
/**
* Returns the next element in the iteration.
*
* @return the next element in the iteration.
* @throws NoSuchElementException
* iteration has no more elements.
*/
public Object next() {
throw new NoSuchElementException("This iterator is empty.");
}
/**
* Removes from the underlying collection the last element returned by the
* iterator (optional operation). This method can be called only once per
* call to <tt>next</tt>. The behavior of an iterator is unspecified if
* the underlying collection is modified while the iteration is in progress
* in any way other than by calling this method.
*
* @throws UnsupportedOperationException
* if the <tt>remove</tt> operation is not supported by this
* Iterator.
* @throws IllegalStateException
* if the <tt>next</tt> method has not yet been called, or the
* <tt>remove</tt> method has already been called after the last
* call to the <tt>next</tt> method.
*/
public void remove() {
throw new UnsupportedOperationException("This iterator is empty, no remove supported.");
}
}
/**
* A singleton instance of the empty iterator. This object can be safely
* shared.
*/
private static final Iterator EMPTY_ITERATOR = new EmptyIterator();
/**
* The underlying storage.
*/
private HashMap table;
/**
* An empty array.
*/
private static final Object[] EMPTY_ARRAY = new Object[0];
/**
* Default constructor.
*/
public HashNMap() {
this.table = new HashMap();
}
/**
* Returns a new empty list.
*
* @return A new empty list.
*/
protected List createList() {
return new ArrayList();
}
/**
* Inserts a new key/value pair into the map. If such a pair already exists,
* it gets replaced with the given values.
*
* @param key
* the key.
* @param val
* the value.
* @return A boolean.
*/
public boolean put(final Object key, final Object val) {
final List v = (List) this.table.get(key);
if (v == null) {
final List newList = createList();
newList.add(val);
this.table.put(key, newList);
return true;
} else {
v.clear();
return v.add(val);
}
}
/**
* Adds a new key/value pair into this map. If the key is not yet in the map,
* it gets added to the map and the call is equal to put(Object,Object).
*
* @param key
* the key.
* @param val
* the value.
* @return true, if the value has been added, false otherwise
*/
public boolean add(final Object key, final Object val) {
final List v = (List) this.table.get(key);
if (v == null) {
put(key, val);
return true;
} else {
return v.add(val);
}
}
/**
* Retrieves the first value registered for an key or null if there was no
* such key in the list.
*
* @param key
* the key.
* @return the value.
*/
public Object getFirst(final Object key) {
return get(key, 0);
}
/**
* Retrieves the n-th value registered for an key or null if there was no such
* key in the list. An index out of bounds exception is thrown if there are
* less than n elements registered to this key.
*
* @param key
* the key.
* @param n
* the index.
* @return the object.
*/
public Object get(final Object key, final int n) {
final List v = (List) this.table.get(key);
if (v == null) {
return null;
}
return v.get(n);
}
/**
* Returns an iterator over all elements registered to the given key.
*
* @param key
* the key.
* @return an iterator.
*/
public Iterator getAll(final Object key) {
final List v = (List) this.table.get(key);
if (v == null) {
return EMPTY_ITERATOR;
}
return v.iterator();
}
/**
* Returns all registered keys as an enumeration.
*
* @return an enumeration of the keys.
*/
public Iterator keys() {
return this.table.keySet().iterator();
}
/**
* Returns all registered keys as set.
*
* @return a set of keys.
*/
public Set keySet() {
return this.table.keySet();
}
/**
* Removes the key/value pair from the map. If the removed entry was the last
* entry for this key, the key gets also removed.
*
* @param key
* the key.
* @param value
* the value.
* @return true, if removing the element was successfull, false otherwise.
*/
public boolean remove(final Object key, final Object value) {
final List v = (List) this.table.get(key);
if (v == null) {
return false;
}
if (!v.remove(value)) {
return false;
}
if (v.size() == 0) {
this.table.remove(key);
}
return true;
}
/**
* Removes all elements for the given key.
*
* @param key
* the key.
*/
public void removeAll(final Object key) {
this.table.remove(key);
}
/**
* Clears all keys and values of this map.
*/
public void clear() {
this.table.clear();
}
/**
* Tests whether this map contains the given key.
*
* @param key
* the key.
* @return true if the key is contained in the map
*/
public boolean containsKey(final Object key) {
return this.table.containsKey(key);
}
/**
* Tests whether this map contains the given value.
*
* @param value
* the value.
* @return true if the value is registered in the map for an key.
*/
public boolean containsValue(final Object value) {
final Iterator e = this.table.values().iterator();
boolean found = false;
while (e.hasNext() && !found) {
final List v = (List) e.next();
found = v.contains(value);
}
return found;
}
/**
* Tests whether this map contains the given value.
*
* @param value
* the value.
* @param key
* the key under which to find the value
* @return true if the value is registered in the map for an key.
*/
public boolean containsValue(final Object key, final Object value) {
final List v = (List) this.table.get(key);
if (v == null) {
return false;
}
return v.contains(value);
}
/**
* Tests whether this map contains the given key or value.
*
* @param value
* the value.
* @return true if the key or value is contained in the map
*/
public boolean contains(final Object value) {
if (containsKey(value)) {
return true;
}
return containsValue(value);
}
/**
* Returns a clone of the specified object, if it can be cloned, otherwise
* throws a CloneNotSupportedException.
*
* @param object
* the object to clone (<code>null</code> not permitted).
* @return A clone of the specified object.
* @throws CloneNotSupportedException
* if the object cannot be cloned.
*/
public static Object clone(final Object object) throws CloneNotSupportedException {
if (object == null) {
throw new IllegalArgumentException("Null 'object' argument.");
}
else {
try {
final Method method = object.getClass().getMethod("clone", (Class[]) null);
if (Modifier.isPublic(method.getModifiers())) {
return method.invoke(object, (Object[]) null);
}
} catch (Exception e) {
}
}
throw new CloneNotSupportedException("Failed to clone.");
}
/**
* Creates a deep copy of this HashNMap.
*
* @return a clone.
* @throws CloneNotSupportedException
* this should never happen.
*/
public Object clone() throws CloneNotSupportedException {
final HashNMap map = (HashNMap) super.clone();
map.table = new HashMap();
final Iterator iterator = keys();
while (iterator.hasNext()) {
final Object key = iterator.next();
final List list = (List) map.table.get(key);
if (list != null) {
map.table.put(key,clone(list));
}
}
return map;
}
/**
* Returns the contents for the given key as object array. If there were no
* objects registered with that key, an empty object array is returned.
*
* @param key
* the key.
* @param data
* the object array to receive the contents.
* @return the contents.
*/
public Object[] toArray(final Object key, final Object[] data) {
if (key == null) {
throw new NullPointerException("Key must not be null.");
}
final List list = (List) this.table.get(key);
if (list != null) {
return list.toArray(data);
}
if (data.length > 0) {
data[0] = null;
}
return data;
}
/**
* Returns the contents for the given key as object array. If there were no
* objects registered with that key, an empty object array is returned.
*
* @param key
* the key.
* @return the contents.
*/
public Object[] toArray(final Object key) {
if (key == null) {
throw new NullPointerException("Key must not be null.");
}
final List list = (List) this.table.get(key);
if (list != null) {
return list.toArray();
}
return EMPTY_ARRAY;
}
/**
* Returns the number of elements registered with the given key.
*
* @param key
* the key.
* @return the number of element for this key, or 0 if there are no elements
* registered.
*/
public int getValueCount(final Object key) {
if (key == null) {
throw new NullPointerException("Key must not be null.");
}
final List list = (List) this.table.get(key);
if (list != null) {
return list.size();
}
return 0;
}
}
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