de.intarsys.tools.collection.IntHashMap Maven / Gradle / Ivy
Show all versions of isrt Show documentation
/*
* Copyright (c) 2007, intarsys consulting GmbH
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* - Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
*
* - Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* - Neither the name of intarsys nor the names of its contributors may be used
* to endorse or promote products derived from this software without specific
* prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
package de.intarsys.tools.collection;
/**
*
* A hash map that uses primitive ints for the key rather than objects.
*
*
*
* Copied from Jakarta Commons Lang internal implementation. To be removed as
* soon as Jakarta Commons Collections provides it.
*
*/
public class IntHashMap {
/**
* The hash table data.
*/
private transient Entry[] table;
/**
* The total number of entries in the hash table.
*/
private transient int count;
/**
* The table is rehashed when its size exceeds this threshold. (The value of
* this field is (int)(capacity * loadFactor).)
*
* @serial
*/
private int threshold;
/**
* The load factor for the hashtable.
*
* @serial
*/
private float loadFactor;
/**
*
* Innerclass that acts as a datastructure to create a new entry in the
* table.
*
*/
private static class Entry {
int hash;
int key;
Object value;
Entry next;
/**
*
* Create a new entry with the given values.
*
*
* @param hash
* The code used to hash the object with
* @param key
* The key used to enter this in the table
* @param value
* The value for this key
* @param next
* A reference to the next entry in the table
*/
protected Entry(int hash, int key, Object value, Entry next) {
this.hash = hash;
this.key = key;
this.value = value;
this.next = next;
}
}
/**
*
* Constructs a new, empty hashtable with a default capacity and load
* factor, which is 20 and 0.75 respectively.
*
*/
public IntHashMap() {
this(20, 0.75f);
}
/**
*
* Constructs a new, empty hashtable with the specified initial capacity and
* default load factor, which is 0.75.
*
*
* @param initialCapacity
* the initial capacity of the hashtable.
* @throws IllegalArgumentException
* if the initial capacity is less than zero.
*/
public IntHashMap(int initialCapacity) {
this(initialCapacity, 0.75f);
}
/**
*
* Constructs a new, empty hashtable with the specified initial capacity and
* the specified load factor.
*
*
* @param initialCapacity
* the initial capacity of the hashtable.
* @param loadFactor
* the load factor of the hashtable.
* @throws IllegalArgumentException
* if the initial capacity is less than zero, or if the load
* factor is nonpositive.
*/
public IntHashMap(int initialCapacity, float loadFactor) {
super();
if (initialCapacity < 0) {
throw new IllegalArgumentException("Illegal Capacity: "
+ initialCapacity);
}
if (loadFactor <= 0) {
throw new IllegalArgumentException("Illegal Load: " + loadFactor);
}
if (initialCapacity == 0) {
initialCapacity = 1;
}
this.loadFactor = loadFactor;
table = new Entry[initialCapacity];
threshold = (int) (initialCapacity * loadFactor);
}
/**
*
* Returns the number of keys in this hashtable.
*
*
* @return the number of keys in this hashtable.
*/
public int size() {
return count;
}
/**
*
* Tests if this hashtable maps no keys to values.
*
*
* @return true if this hashtable maps no keys to values;
* false otherwise.
*/
public boolean isEmpty() {
return count == 0;
}
/**
*
* Tests if some key maps into the specified value in this hashtable. This
* operation is more expensive than the containsKey method.
*
*
*
* Note that this method is identical in functionality to containsValue,
* (which is part of the Map interface in the collections framework).
*
*
* @param value
* a value to search for.
* @return true if and only if some key maps to the
* value argument in this hashtable as determined by
* the equals method; false otherwise.
* @throws NullPointerException
* if the value is null.
* @see #containsKey(int)
* @see #containsValue(Object)
* @see java.util.Map
*/
public boolean contains(Object value) {
if (value == null) {
throw new NullPointerException();
}
Entry[] tab = table;
for (int i = tab.length; i-- > 0;) {
for (Entry e = tab[i]; e != null; e = e.next) {
if (e.value.equals(value)) {
return true;
}
}
}
return false;
}
/**
*
* Returns true if this HashMap maps one or more keys to this
* value.
*
*
*
* Note that this method is identical in functionality to contains (which
* predates the Map interface).
*
*
* @param value
* value whose presence in this HashMap is to be tested.
* @return boolean true if the value is contained
* @see java.util.Map
* @since JDK1.2
*/
public boolean containsValue(Object value) {
return contains(value);
}
/**
*
* Tests if the specified object is a key in this hashtable.
*
*
* @param key
* possible key.
* @return true if and only if the specified object is a key
* in this hashtable, as determined by the equals method;
* false otherwise.
* @see #contains(Object)
*/
public boolean containsKey(int key) {
Entry[] tab = table;
int hash = key;
int index = (hash & 0x7FFFFFFF) % tab.length;
for (Entry e = tab[index]; e != null; e = e.next) {
if (e.hash == hash) {
return true;
}
}
return false;
}
/**
*
* Returns the value to which the specified key is mapped in this map.
*
*
* @param key
* a key in the hashtable.
* @return the value to which the key is mapped in this hashtable;
* null if the key is not mapped to any value in this
* hashtable.
* @see #put(int, Object)
*/
public Object get(int key) {
Entry[] tab = table;
int hash = key;
int index = (hash & 0x7FFFFFFF) % tab.length;
for (Entry e = tab[index]; e != null; e = e.next) {
if (e.hash == hash) {
return e.value;
}
}
return null;
}
/**
*
* Increases the capacity of and internally reorganizes this hashtable, in
* order to accommodate and access its entries more efficiently.
*
*
*
* This method is called automatically when the number of keys in the
* hashtable exceeds this hashtable's capacity and load factor.
*
*/
protected void rehash() {
int oldCapacity = table.length;
Entry[] oldMap = table;
int newCapacity = (oldCapacity * 2) + 1;
Entry[] newMap = new Entry[newCapacity];
threshold = (int) (newCapacity * loadFactor);
table = newMap;
for (int i = oldCapacity; i-- > 0;) {
for (Entry old = oldMap[i]; old != null;) {
Entry e = old;
old = old.next;
int index = (e.hash & 0x7FFFFFFF) % newCapacity;
e.next = newMap[index];
newMap[index] = e;
}
}
}
/**
*
* Maps the specified key to the specified value
* in this hashtable. The key cannot be null.
*
*
*
* The value can be retrieved by calling the get method with
* a key that is equal to the original key.
*
*
* @param key
* the hashtable key.
* @param value
* the value.
* @return the previous value of the specified key in this hashtable, or
* null if it did not have one.
* @throws NullPointerException
* if the key is null.
* @see #get(int)
*/
public Object put(int key, Object value) {
// Makes sure the key is not already in the hashtable.
Entry[] tab = table;
int hash = key;
int index = (hash & 0x7FFFFFFF) % tab.length;
for (Entry e = tab[index]; e != null; e = e.next) {
if (e.hash == hash) {
Object old = e.value;
e.value = value;
return old;
}
}
if (count >= threshold) {
// Rehash the table if the threshold is exceeded
rehash();
tab = table;
index = (hash & 0x7FFFFFFF) % tab.length;
}
// Creates the new entry.
Entry e = new Entry(hash, key, value, tab[index]);
tab[index] = e;
count++;
return null;
}
/**
*
* Removes the key (and its corresponding value) from this hashtable.
*
*
*
* This method does nothing if the key is not present in the hashtable.
*
*
* @param key
* the key that needs to be removed.
* @return the value to which the key had been mapped in this hashtable, or
* null if the key did not have a mapping.
*/
public Object remove(int key) {
Entry[] tab = table;
int hash = key;
int index = (hash & 0x7FFFFFFF) % tab.length;
for (Entry e = tab[index], prev = null; e != null; prev = e, e = e.next) {
if (e.hash == hash) {
if (prev != null) {
prev.next = e.next;
} else {
tab[index] = e.next;
}
count--;
Object oldValue = e.value;
e.value = null;
return oldValue;
}
}
return null;
}
/**
*
* Clears this hashtable so that it contains no keys.
*
*/
public synchronized void clear() {
Entry[] tab = table;
for (int index = tab.length; --index >= 0;) {
tab[index] = null;
}
count = 0;
}
}