inthashmap.java

Wicket一个开发Java Web应用程序框架。它使得开发web应用程序变得容易而轻松。 Wicket利用一个POJO data beans组件使得它可以与任何持久层技术相结合。

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.wicket.util.collections;

import java.io.IOException;
import java.io.Serializable;
import java.util.AbstractCollection;
import java.util.AbstractSet;
import java.util.Collection;
import java.util.ConcurrentModificationException;
import java.util.Iterator;
import java.util.Map;
import java.util.NoSuchElementException;
import java.util.Set;

/**
 * This is an integer hashmap that has the exact same features and interface as a normal Map except
 * that the key is directly an integer. So no hash is calculated or key object is stored.
 * 
 * @author jcompagner
 */
public class IntHashMap implements Cloneable, Serializable
{
	transient volatile Set keySet = null;

	transient volatile Collection values = null;

	/**
	 * The default initial capacity - MUST be a power of two.
	 */
	static final int DEFAULT_INITIAL_CAPACITY = 16;

	/**
	 * The maximum capacity, used if a higher value is implicitly specified by either of the
	 * constructors with arguments. MUST be a power of two <= 1<<30.
	 */
	static final int MAXIMUM_CAPACITY = 1 << 30;

	/**
	 * The load factor used when none specified in constructor.
	 */
	static final float DEFAULT_LOAD_FACTOR = 0.75f;

	/**
	 * The table, resized as necessary. Length MUST Always be a power of two.
	 */
	transient Entry[] table;

	/**
	 * The number of key-value mappings contained in this identity hash map.
	 */
	transient int size;

	/**
	 * The next size value at which to resize (capacity * load factor).
	 * 
	 * @serial
	 */
	int threshold;

	/**
	 * The load factor for the hash table.
	 * 
	 * @serial
	 */
	final float loadFactor;

	/**
	 * The number of times this HashMap has been structurally modified Structural modifications are
	 * those that change the number of mappings in the HashMap or otherwise modify its internal
	 * structure (e.g., rehash). This field is used to make iterators on Collection-views of the
	 * HashMap fail-fast. (See ConcurrentModificationException).
	 */
	transient volatile int modCount;

	/**
	 * Constructs an empty <tt>HashMap</tt> with the specified initial capacity and load factor.
	 * 
	 * @param initialCapacity
	 *            The initial capacity.
	 * @param loadFactor
	 *            The load factor.
	 * @throws IllegalArgumentException
	 *             if the initial capacity is negative or the load factor is nonpositive.
	 */
	public IntHashMap(int initialCapacity, float loadFactor)
	{
		if (initialCapacity < 0)
		{
			throw new IllegalArgumentException("Illegal initial capacity: " + //$NON-NLS-1$
					initialCapacity);
		}
		if (initialCapacity > MAXIMUM_CAPACITY)
		{
			initialCapacity = MAXIMUM_CAPACITY;
		}
		if (loadFactor <= 0 || Float.isNaN(loadFactor))
		{
			throw new IllegalArgumentException("Illegal load factor: " + //$NON-NLS-1$
					loadFactor);
		}

		// Find a power of 2 >= initialCapacity
		int capacity = 1;
		while (capacity < initialCapacity)
		{
			capacity <<= 1;
		}

		this.loadFactor = loadFactor;
		threshold = (int)(capacity * loadFactor);
		table = new Entry[capacity];
		init();
	}

	/**
	 * Constructs an empty <tt>HashMap</tt> with the specified initial capacity and the default
	 * load factor (0.75).
	 * 
	 * @param initialCapacity
	 *            the initial capacity.
	 * @throws IllegalArgumentException
	 *             if the initial capacity is negative.
	 */
	public IntHashMap(int initialCapacity)
	{
		this(initialCapacity, DEFAULT_LOAD_FACTOR);
	}

	/**
	 * Constructs an empty <tt>HashMap</tt> with the default initial capacity (16) and the default
	 * load factor (0.75).
	 */
	public IntHashMap()
	{
		loadFactor = DEFAULT_LOAD_FACTOR;
		threshold = (int)(DEFAULT_INITIAL_CAPACITY * DEFAULT_LOAD_FACTOR);
		table = new Entry[DEFAULT_INITIAL_CAPACITY];
		init();
	}

	// internal utilities

	/**
	 * Initialization hook for subclasses. This method is called in all constructors and
	 * pseudo-constructors (clone, readObject) after HashMap has been initialized but before any
	 * entries have been inserted. (In the absence of this method, readObject would require explicit
	 * knowledge of subclasses.)
	 */
	void init()
	{
	}

	/**
	 * Returns index for hash code h.
	 * 
	 * @param h
	 * @param length
	 * @return The index for the hash integer for the given length
	 */
	static int indexFor(int h, int length)
	{
		return h & (length - 1);
	}

	/**
	 * Returns the number of key-value mappings in this map.
	 * 
	 * @return the number of key-value mappings in this map.
	 */
	public int size()
	{
		return size;
	}

	/**
	 * Returns <tt>true</tt> if this map contains no key-value mappings.
	 * 
	 * @return <tt>true</tt> if this map contains no key-value mappings.
	 */
	public boolean isEmpty()
	{
		return size == 0;
	}

	/**
	 * Returns the value to which the specified key is mapped in this identity hash map, or
	 * <tt>null</tt> if the map contains no mapping for this key. A return value of <tt>null</tt>
	 * does not <i>necessarily</i> indicate that the map contains no mapping for the key; it is
	 * also possible that the map explicitly maps the key to <tt>null</tt>. The
	 * <tt>containsKey</tt> method may be used to distinguish these two cases.
	 * 
	 * @param key
	 *            the key whose associated value is to be returned.
	 * @return the value to which this map maps the specified key, or <tt>null</tt> if the map
	 *         contains no mapping for this key.
	 * @see #put(int, Object)
	 */
	public Object get(int key)
	{
		int i = indexFor(key, table.length);
		Entry e = table[i];
		while (true)
		{
			if (e == null)
			{
				return e;
			}
			if (key == e.key)
			{
				return e.value;
			}
			e = e.next;
		}
	}

	/**
	 * Returns <tt>true</tt> if this map contains a mapping for the specified key.
	 * 
	 * @param key
	 *            The key whose presence in this map is to be tested
	 * @return <tt>true</tt> if this map contains a mapping for the specified key.
	 */
	public boolean containsKey(int key)
	{
		int i = indexFor(key, table.length);
		Entry e = table[i];
		while (e != null)
		{
			if (key == e.key)
			{
				return true;
			}
			e = e.next;
		}
		return false;
	}

	/**
	 * Returns the entry associated with the specified key in the HashMap. Returns null if the
	 * HashMap contains no mapping for this key.
	 * 
	 * @param key
	 * @return The Entry object for the given hash key
	 */
	Entry getEntry(int key)
	{
		int i = indexFor(key, table.length);
		Entry e = table[i];
		while (e != null && !(key == e.key))
		{
			e = e.next;
		}
		return e;
	}

	/**
	 * Associates the specified value with the specified key in this map. If the map previously
	 * contained a mapping for this key, the old value is replaced.
	 * 
	 * @param key
	 *            key with which the specified value is to be associated.
	 * @param value
	 *            value to be associated with the specified key.
	 * @return previous value associated with specified key, or <tt>null</tt> if there was no
	 *         mapping for key. A <tt>null</tt> return can also indicate that the HashMap
	 *         previously associated <tt>null</tt> with the specified key.
	 */
	public Object put(int key, Object value)
	{
		int i = indexFor(key, table.length);

		for (Entry e = table[i]; e != null; e = e.next)
		{
			if (key == e.key)
			{
				Object oldValue = e.value;
				e.value = value;
				return oldValue;
			}
		}

		modCount++;
		addEntry(key, value, i);
		return null;
	}

	/**
	 * This method is used instead of put by constructors and pseudoconstructors (clone,
	 * readObject). It does not resize the table, check for comodification, etc. It calls
	 * createEntry rather than addEntry.
	 * 
	 * @param key
	 * @param value
	 */
	private void putForCreate(int key, Object value)
	{
		int i = indexFor(key, table.length);

		/**
		 * Look for preexisting entry for key. This will never happen for clone or deserialize. It
		 * will only happen for construction if the input Map is a sorted map whose ordering is
		 * inconsistent w/ equals.
		 */
		for (Entry e = table[i]; e != null; e = e.next)
		{
			if (key == e.key)
			{
				e.value = value;
				return;
			}
		}

		createEntry(key, value, i);
	}

	void putAllForCreate(IntHashMap m)
	{
		for (Iterator i = m.entrySet().iterator(); i.hasNext();)
		{
			Entry e = (Entry)i.next();
			putForCreate(e.getKey(), e.getValue());
		}
	}

	/**
	 * Rehashes the contents of this map into a new array with a larger capacity. This method is
	 * called automatically when the number of keys in this map reaches its threshold.
	 * 
	 * If current capacity is MAXIMUM_CAPACITY, this method does not resize the map, but but sets
	 * threshold to Integer.MAX_VALUE. This has the effect of preventing future calls.
	 * 
	 * @param newCapacity
	 *            the new capacity, MUST be a power of two; must be greater than current capacity
	 *            unless current capacity is MAXIMUM_CAPACITY (in which case value is irrelevant).
	 */
	void resize(int newCapacity)
	{
		Entry[] oldTable = table;
		int oldCapacity = oldTable.length;
		if (oldCapacity == MAXIMUM_CAPACITY)
		{
			threshold = Integer.MAX_VALUE;
			return;
		}

		Entry[] newTable = new Entry[newCapacity];
		transfer(newTable);
		table = newTable;
		threshold = (int)(newCapacity * loadFactor);
	}

	/**
	 * Transfer all entries from current table to newTable.
	 * 
	 * @param newTable
	 */
	void transfer(Entry[] newTable)
	{
		Entry[] src = table;
		int newCapacity = newTable.length;
		for (int j = 0; j < src.length; j++)
		{
			Entry e = src[j];
			if (e != null)
			{
				src[j] = null;
				do
				{
					Entry next = e.next;
					int i = indexFor(e.key, newCapacity);
					e.next = newTable[i];
					newTable[i] = e;
					e = next;
				}
				while (e != null);
			}
		}
	}

	/**
	 * Copies all of the mappings from the specified map to this map These mappings will replace any
	 * mappings that this map had for any of the keys currently in the specified map.
	 * 
	 * @param m
	 *            mappings to be stored in this map.
	 * @throws NullPointerException
	 *             if the specified map is null.
	 */
	public void putAll(IntHashMap m)
	{
		int numKeysToBeAdded = m.size();
		if (numKeysToBeAdded == 0)
		{
			return;
		}

		/*
		 * Expand the map if the map if the number of mappings to be added is greater than or equal
		 * to threshold. This is conservative; the obvious condition is (m.size() + size) >=
		 * threshold, but this condition could result in a map with twice the appropriate capacity,
		 * if the keys to be added overlap with the keys already in this map. By using the
		 * conservative calculation, we subject ourself to at most one extra resize.
		 */
		if (numKeysToBeAdded > threshold)
		{
			int targetCapacity = (int)(numKeysToBeAdded / loadFactor + 1);
			if (targetCapacity > MAXIMUM_CAPACITY)
			{
				targetCapacity = MAXIMUM_CAPACITY;
			}
			int newCapacity = table.length;
			while (newCapacity < targetCapacity)
			{
				newCapacity <<= 1;
			}
			if (newCapacity > table.length)
			{
				resize(newCapacity);
			}
		}

		for (Iterator i = m.entrySet().iterator(); i.hasNext();)
		{
			Entry e = (Entry)i.next();
			put(e.getKey(), e.getValue());
		}
	}

	/**
	 * Removes the mapping for this key from this map if present.
	 * 
	 * @param key
	 *            key whose mapping is to be removed from the map.
	 * @return previous value associated with specified key, or <tt>null</tt> if there was no
	 *         mapping for key. A <tt>null</tt> return can also indicate that the map previously
	 *         associated <tt>null</tt> with the specified key.
	 */
	public Object remove(int key)
	{
		Entry e = removeEntryForKey(key);
		return (e == null ? e : e.value);
	}

	/**
	 * Removes and returns the entry associated with the specified key in the HashMap. Returns null
	 * if the HashMap contains no mapping for this key.
	 * 
	 * @param key
	 * @return The Entry object that was removed
	 */
	Entry removeEntryForKey(int key)
	{
		int i = indexFor(key, table.length);
		Entry prev = table[i];
		Entry e = prev;

		while (e != null)
		{
			Entry next = e.next;
			if (key == e.key)
			{
				modCount++;
				size--;
				if (prev == e)
				{
					table[i] = next;
				}
				else
				{
					prev.next = next;
				}
				return e;
			}
			prev = e;
			e = next;
		}

		return e;
	}

	/**
	 * Special version of remove for EntrySet.
	 * 
	 * @param o
	 * @return The entry that was removed
	 */
	Entry removeMapping(Object o)
	{
		if (!(o instanceof Entry))
		{
			return null;
		}

		Entry entry = (Entry)o;
		int key = entry.getKey();
		int i = indexFor(key, table.length);
		Entry prev = table[i];
		Entry e = prev;

		while (e != null)
		{
			Entry next = e.next;
			if (e.key == key && e.equals(entry))
			{
				modCount++;
				size--;
				if (prev == e)
				{
					table[i] = next;
				}
				else
				{
					prev.next = next;
				}
				return e;
			}
			prev = e;
			e = next;
		}

		return e;
	}

	/**
	 * Removes all mappings from this map.
	 */
	public void clear()
	{
		modCount++;
		Entry tab[] = table;
		for (int i = 0; i < tab.length; i++)
		{
			tab[i] = null;
		}
		size = 0;
	}

	/**
	 * Returns <tt>true</tt> if this map maps one or more keys to the specified value.
	 * 
	 * @param value
	 *            value whose presence in this map is to be tested.
	 * @return <tt>true</tt> if this map maps one or more keys to the specified value.
	 */
	public boolean containsValue(Object value)
	{
		if (value == null)
		{
			return containsNullValue();
		}

		Entry tab[] = table;
		for (int i = 0; i < tab.length; i++)
		{
			for (Entry e = tab[i]; e != null; e = e.next)
			{
				if (value.equals(e.value))
				{