org.javimmutable.collections.hash.JImmutableHashMap Maven / Gradle / Ivy
Go to download
Show more of this group Show more artifacts with this name
Show all versions of javimmutable-collections Show documentation
Show all versions of javimmutable-collections Show documentation
Library providing immutable/persistent collection classes for
Java. While collections are immutable they provide methods for
adding and removing values by creating new modified copies of
themselves. Each copy shares almost all of its structure with
other copies to minimize memory consumption.
///###////////////////////////////////////////////////////////////////////////
//
// Burton Computer Corporation
// http://www.burton-computer.com
//
// Copyright (c) 2014, Burton Computer Corporation
// All rights reserved.
//
// 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 the Burton Computer Corporation 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
// HOLDER 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 org.javimmutable.collections.hash;
import org.javimmutable.collections.Cursor;
import org.javimmutable.collections.Holder;
import org.javimmutable.collections.Holders;
import org.javimmutable.collections.JImmutableMap;
import org.javimmutable.collections.MapEntry;
import org.javimmutable.collections.array.trie32.EmptyTrieNode;
import org.javimmutable.collections.array.trie32.Transforms;
import org.javimmutable.collections.array.trie32.TrieNode;
import org.javimmutable.collections.common.AbstractJImmutableMap;
import org.javimmutable.collections.common.MutableDelta;
public class JImmutableHashMap
extends AbstractJImmutableMap
{
// we only need one instance of the transformations object
static final HashValueListTransforms LIST_TRANSFORMS = new HashValueListTransforms();
// we only need one instance of the transformations object
static final HashValueTreeTransforms TREE_TRANSFORMS = new HashValueTreeTransforms();
// this is safe since the transformations object works for any possible K and V
@SuppressWarnings("unchecked")
static final JImmutableHashMap LIST_EMPTY = new JImmutableHashMap(EmptyTrieNode.of(), 0, LIST_TRANSFORMS);
// this is safe since the transformations object works for any possible K and V
@SuppressWarnings("unchecked")
static final JImmutableHashMap TREE_EMPTY = new JImmutableHashMap(EmptyTrieNode.of(), 0, TREE_TRANSFORMS);
private final TrieNode root;
private final int size;
private final Transforms transforms;
private JImmutableHashMap(TrieNode root,
int size,
Transforms transforms)
{
this.root = root;
this.size = size;
this.transforms = transforms;
}
/**
* Returns an empty hash map. The empty map will automatically select a collision handling strategy
* on the first call to assign() based on the key for that call. For this reason all keys used for a
* given map must either implement or not implement Comparable. If some keys implement it and some do
* not the collision handling code will likely fail due to a class cast exception or a method
* not defined exception.
*
* @param
* @param
* @return
*/
@SuppressWarnings("unchecked")
public static EmptyHashMap of()
{
return (EmptyHashMap)EmptyHashMap.INSTANCE;
}
/**
* Returns an empty map using the appropriate collision handling strategy for keys of the given
* class. All keys used with that map should derive from the specified class to avoid runtime
* problems with incompatible keys.
*
* @param klass
* @param
* @param
* @return
*/
@SuppressWarnings("unchecked")
public static JImmutableMap of(Class klass)
{
return klass.isAssignableFrom(Comparable.class) ? TREE_EMPTY : LIST_EMPTY;
}
/**
* Returns an empty map using the appropriate collision handling strategy for the given key's
* class. All keys used with that map should derive from the specified key's class to avoid runtime
* problems with incompatible keys.
*
* @param key
* @param
* @param
* @return
*/
@SuppressWarnings("unchecked")
public static JImmutableMap forKey(K key)
{
return (key instanceof Comparable) ? TREE_EMPTY : LIST_EMPTY;
}
/**
* Returns an empty map using linked lists for handling hash code collisions. This is safe
* for any type of key but is slower when many keys have the same hash code.
*
* @param
* @param
* @return
*/
@SuppressWarnings("unchecked")
public static JImmutableMap usingList()
{
return (JImmutableMap)LIST_EMPTY;
}
/**
* Returns an empty map using linked lists for handling hash code collisions. This is faster
* than the list based collision handling but depends on all keys implementing Comparable and
* being able to compare themselves to all other keys.
*
* @param
* @param
* @return
*/
@SuppressWarnings("unchecked")
public static , V> JImmutableMap usingTree()
{
return (JImmutableMap)TREE_EMPTY;
}
@Override
public V getValueOr(K key,
V defaultValue)
{
return root.getValueOr(TrieNode.ROOT_SHIFT, key.hashCode(), key, transforms, defaultValue);
}
@Override
public Holder find(K key)
{
return root.find(TrieNode.ROOT_SHIFT, key.hashCode(), key, transforms);
}
@Override
public Holder> findEntry(K key)
{
Holder value = find(key);
if (value.isEmpty()) {
return Holders.of();
} else {
return Holders.>of(MapEntry.of(key, value.getValue()));
}
}
@Override
public JImmutableMap assign(K key,
V value)
{
MutableDelta sizeDelta = new MutableDelta();
TrieNode newRoot = root.assign(TrieNode.ROOT_SHIFT, key.hashCode(), key, value, transforms, sizeDelta);
if (newRoot == root) {
return this;
} else {
return new JImmutableHashMap(newRoot, size + sizeDelta.getValue(), transforms);
}
}
@Override
public JImmutableMap delete(K key)
{
MutableDelta sizeDelta = new MutableDelta();
TrieNode newRoot = root.delete(TrieNode.ROOT_SHIFT, key.hashCode(), key, transforms, sizeDelta);
if (newRoot == root) {
return this;
} else if (newRoot.isEmpty()) {
return of();
} else {
return new JImmutableHashMap(newRoot, size + sizeDelta.getValue(), transforms);
}
}
@Override
public int size()
{
return size;
}
@Override
public JImmutableMap deleteAll()
{
return of();
}
@Override
public Cursor> cursor()
{
return root.anyOrderEntryCursor(transforms);
}
// for unit test to verify proper transforms selected
Transforms getTransforms()
{
return transforms;
}
}