org.apache.commons.collections4.map.AbstractHashedMap Maven / Gradle / Ivy
/*
* 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.commons.collections4.map;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.util.AbstractCollection;
import java.util.AbstractMap;
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;
import org.apache.commons.collections4.IterableMap;
import org.apache.commons.collections4.KeyValue;
import org.apache.commons.collections4.MapIterator;
import org.apache.commons.collections4.iterators.EmptyIterator;
import org.apache.commons.collections4.iterators.EmptyMapIterator;
/**
* An abstract implementation of a hash-based map which provides numerous points for
* subclasses to override.
*
* This class implements all the features necessary for a subclass hash-based map.
* Key-value entries are stored in instances of the HashEntry class,
* which can be overridden and replaced. The iterators can similarly be replaced,
* without the need to replace the KeySet, EntrySet and Values view classes.
*
* Overridable methods are provided to change the default hashing behaviour, and
* to change how entries are added to and removed from the map. Hopefully, all you
* need for unusual subclasses is here.
*
* NOTE: From Commons Collections 3.1 this class extends AbstractMap.
* This is to provide backwards compatibility for ReferenceMap between v3.0 and v3.1.
* This extends clause will be removed in v5.0.
*
* @param the type of the keys in this map
* @param the type of the values in this map
* @since 3.0
*/
public class AbstractHashedMap extends AbstractMap implements IterableMap {
protected static final String NO_NEXT_ENTRY = "No next() entry in the iteration";
protected static final String NO_PREVIOUS_ENTRY = "No previous() entry in the iteration";
protected static final String REMOVE_INVALID = "remove() can only be called once after next()";
protected static final String GETKEY_INVALID = "getKey() can only be called after next() and before remove()";
protected static final String GETVALUE_INVALID = "getValue() can only be called after next() and before remove()";
protected static final String SETVALUE_INVALID = "setValue() can only be called after next() and before remove()";
/** The default capacity to use */
protected static final int DEFAULT_CAPACITY = 16;
/** The default threshold to use */
protected static final int DEFAULT_THRESHOLD = 12;
/** The default load factor to use */
protected static final float DEFAULT_LOAD_FACTOR = 0.75f;
/** The maximum capacity allowed */
protected static final int MAXIMUM_CAPACITY = 1 << 30;
/** An object for masking null */
protected static final Object NULL = new Object();
/** Load factor, normally 0.75 */
transient float loadFactor;
/** The size of the map */
transient int size;
/** Map entries */
transient HashEntry[] data;
/** Size at which to rehash */
transient int threshold;
/** Modification count for iterators */
transient int modCount;
/** Entry set */
transient EntrySet entrySet;
/** Key set */
transient KeySet keySet;
/** Values */
transient Values values;
/**
* Constructor only used in deserialization, do not use otherwise.
*/
protected AbstractHashedMap() {
super();
}
/**
* Constructor which performs no validation on the passed in parameters.
*
* @param initialCapacity the initial capacity, must be a power of two
* @param loadFactor the load factor, must be > 0.0f and generally < 1.0f
* @param threshold the threshold, must be sensible
*/
@SuppressWarnings("unchecked")
protected AbstractHashedMap(final int initialCapacity, final float loadFactor, final int threshold) {
super();
this.loadFactor = loadFactor;
this.data = new HashEntry[initialCapacity];
this.threshold = threshold;
init();
}
/**
* Constructs a new, empty map with the specified initial capacity and
* default load factor.
*
* @param initialCapacity the initial capacity
* @throws IllegalArgumentException if the initial capacity is negative
*/
protected AbstractHashedMap(final int initialCapacity) {
this(initialCapacity, DEFAULT_LOAD_FACTOR);
}
/**
* Constructs a new, empty map 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
* @throws IllegalArgumentException if the load factor is less than or equal to zero
*/
@SuppressWarnings("unchecked")
protected AbstractHashedMap(int initialCapacity, final float loadFactor) {
super();
if (initialCapacity < 0) {
throw new IllegalArgumentException("Initial capacity must be a non negative number");
}
if (loadFactor <= 0.0f || Float.isNaN(loadFactor)) {
throw new IllegalArgumentException("Load factor must be greater than 0");
}
this.loadFactor = loadFactor;
initialCapacity = calculateNewCapacity(initialCapacity);
this.threshold = calculateThreshold(initialCapacity, loadFactor);
this.data = new HashEntry[initialCapacity];
init();
}
/**
* Constructor copying elements from another map.
*
* @param map the map to copy
* @throws NullPointerException if the map is null
*/
protected AbstractHashedMap(final Map map) {
this(Math.max(2 * map.size(), DEFAULT_CAPACITY), DEFAULT_LOAD_FACTOR);
_putAll(map);
}
/**
* Initialise subclasses during construction, cloning or deserialization.
*/
protected void init() {
}
//-----------------------------------------------------------------------
/**
* Gets the value mapped to the key specified.
*
* @param key the key
* @return the mapped value, null if no match
*/
@Override
public V get(Object key) {
key = convertKey(key);
final int hashCode = hash(key);
HashEntry entry = data[hashIndex(hashCode, data.length)]; // no local for hash index
while (entry != null) {
if (entry.hashCode == hashCode && isEqualKey(key, entry.key)) {
return entry.getValue();
}
entry = entry.next;
}
return null;
}
/**
* Gets the size of the map.
*
* @return the size
*/
@Override
public int size() {
return size;
}
/**
* Checks whether the map is currently empty.
*
* @return true if the map is currently size zero
*/
@Override
public boolean isEmpty() {
return size == 0;
}
//-----------------------------------------------------------------------
/**
* Checks whether the map contains the specified key.
*
* @param key the key to search for
* @return true if the map contains the key
*/
@Override
public boolean containsKey(Object key) {
key = convertKey(key);
final int hashCode = hash(key);
HashEntry entry = data[hashIndex(hashCode, data.length)]; // no local for hash index
while (entry != null) {
if (entry.hashCode == hashCode && isEqualKey(key, entry.key)) {
return true;
}
entry = entry.next;
}
return false;
}
/**
* Checks whether the map contains the specified value.
*
* @param value the value to search for
* @return true if the map contains the value
*/
@Override
public boolean containsValue(final Object value) {
if (value == null) {
for (final HashEntry element : data) {
HashEntry entry = element;
while (entry != null) {
if (entry.getValue() == null) {
return true;
}
entry = entry.next;
}
}
} else {
for (final HashEntry element : data) {
HashEntry entry = element;
while (entry != null) {
if (isEqualValue(value, entry.getValue())) {
return true;
}
entry = entry.next;
}
}
}
return false;
}
//-----------------------------------------------------------------------
/**
* Puts a key-value mapping into this map.
*
* @param key the key to add
* @param value the value to add
* @return the value previously mapped to this key, null if none
*/
@Override
public V put(final K key, final V value) {
final Object convertedKey = convertKey(key);
final int hashCode = hash(convertedKey);
final int index = hashIndex(hashCode, data.length);
HashEntry entry = data[index];
while (entry != null) {
if (entry.hashCode == hashCode && isEqualKey(convertedKey, entry.key)) {
final V oldValue = entry.getValue();
updateEntry(entry, value);
return oldValue;
}
entry = entry.next;
}
addMapping(index, hashCode, key, value);
return null;
}
/**
* Puts all the values from the specified map into this map.
*
* This implementation iterates around the specified map and
* uses {@link #put(Object, Object)}.
*
* @param map the map to add
* @throws NullPointerException if the map is null
*/
@Override
public void putAll(final Map map) {
_putAll(map);
}
/**
* Puts all the values from the specified map into this map.
*
* This implementation iterates around the specified map and
* uses {@link #put(Object, Object)}.
*
* It is private to allow the constructor to still call it
* even when putAll is overriden.
*
* @param map the map to add
* @throws NullPointerException if the map is null
*/
private void _putAll(final Map map) {
final int mapSize = map.size();
if (mapSize == 0) {
return;
}
final int newSize = (int) ((size + mapSize) / loadFactor + 1);
ensureCapacity(calculateNewCapacity(newSize));
for (final Map.Entry entry: map.entrySet()) {
put(entry.getKey(), entry.getValue());
}
}
/**
* Removes the specified mapping from this map.
*
* @param key the mapping to remove
* @return the value mapped to the removed key, null if key not in map
*/
@Override
public V remove(Object key) {
key = convertKey(key);
final int hashCode = hash(key);
final int index = hashIndex(hashCode, data.length);
HashEntry entry = data[index];
HashEntry previous = null;
while (entry != null) {
if (entry.hashCode == hashCode && isEqualKey(key, entry.key)) {
final V oldValue = entry.getValue();
removeMapping(entry, index, previous);
return oldValue;
}
previous = entry;
entry = entry.next;
}
return null;
}
/**
* Clears the map, resetting the size to zero and nullifying references
* to avoid garbage collection issues.
*/
@Override
public void clear() {
modCount++;
final HashEntry[] data = this.data;
for (int i = data.length - 1; i >= 0; i--) {
data[i] = null;
}
size = 0;
}
//-----------------------------------------------------------------------
/**
* Converts input keys to another object for storage in the map.
* This implementation masks nulls.
* Subclasses can override this to perform alternate key conversions.
*
* The reverse conversion can be changed, if required, by overriding the
* getKey() method in the hash entry.
*
* @param key the key convert
* @return the converted key
*/
protected Object convertKey(final Object key) {
return key == null ? NULL : key;
}
/**
* Gets the hash code for the key specified.
* This implementation uses the additional hashing routine from JDK1.4.
* Subclasses can override this to return alternate hash codes.
*
* @param key the key to get a hash code for
* @return the hash code
*/
protected int hash(final Object key) {
// same as JDK 1.4
int h = key.hashCode();
h += ~(h << 9);
h ^= h >>> 14;
h += h << 4;
h ^= h >>> 10;
return h;
}
/**
* Compares two keys, in internal converted form, to see if they are equal.
* This implementation uses the equals method and assumes neither key is null.
* Subclasses can override this to match differently.
*
* @param key1 the first key to compare passed in from outside
* @param key2 the second key extracted from the entry via entry.key
* @return true if equal
*/
protected boolean isEqualKey(final Object key1, final Object key2) {
return key1 == key2 || key1.equals(key2);
}
/**
* Compares two values, in external form, to see if they are equal.
* This implementation uses the equals method and assumes neither value is null.
* Subclasses can override this to match differently.
*
* @param value1 the first value to compare passed in from outside
* @param value2 the second value extracted from the entry via getValue()
* @return true if equal
*/
protected boolean isEqualValue(final Object value1, final Object value2) {
return value1 == value2 || value1.equals(value2);
}
/**
* Gets the index into the data storage for the hashCode specified.
* This implementation uses the least significant bits of the hashCode.
* Subclasses can override this to return alternate bucketing.
*
* @param hashCode the hash code to use
* @param dataSize the size of the data to pick a bucket from
* @return the bucket index
*/
protected int hashIndex(final int hashCode, final int dataSize) {
return hashCode & dataSize - 1;
}
//-----------------------------------------------------------------------
/**
* Gets the entry mapped to the key specified.
*
* This method exists for subclasses that may need to perform a multi-step
* process accessing the entry. The public methods in this class don't use this
* method to gain a small performance boost.
*
* @param key the key
* @return the entry, null if no match
*/
protected HashEntry getEntry(Object key) {
key = convertKey(key);
final int hashCode = hash(key);
HashEntry entry = data[hashIndex(hashCode, data.length)]; // no local for hash index
while (entry != null) {
if (entry.hashCode == hashCode && isEqualKey(key, entry.key)) {
return entry;
}
entry = entry.next;
}
return null;
}
//-----------------------------------------------------------------------
/**
* Updates an existing key-value mapping to change the value.
*
* This implementation calls setValue() on the entry.
* Subclasses could override to handle changes to the map.
*
* @param entry the entry to update
* @param newValue the new value to store
*/
protected void updateEntry(final HashEntry entry, final V newValue) {
entry.setValue(newValue);
}
/**
* Reuses an existing key-value mapping, storing completely new data.
*
* This implementation sets all the data fields on the entry.
* Subclasses could populate additional entry fields.
*
* @param entry the entry to update, not null
* @param hashIndex the index in the data array
* @param hashCode the hash code of the key to add
* @param key the key to add
* @param value the value to add
*/
protected void reuseEntry(final HashEntry entry, final int hashIndex, final int hashCode,
final K key, final V value) {
entry.next = data[hashIndex];
entry.hashCode = hashCode;
entry.key = key;
entry.value = value;
}
//-----------------------------------------------------------------------
/**
* Adds a new key-value mapping into this map.
*
* This implementation calls createEntry(), addEntry()
* and checkCapacity().
* It also handles changes to modCount and size.
* Subclasses could override to fully control adds to the map.
*
* @param hashIndex the index into the data array to store at
* @param hashCode the hash code of the key to add
* @param key the key to add
* @param value the value to add
*/
protected void addMapping(final int hashIndex, final int hashCode, final K key, final V value) {
modCount++;
final HashEntry entry = createEntry(data[hashIndex], hashCode, key, value);
addEntry(entry, hashIndex);
size++;
checkCapacity();
}
/**
* Creates an entry to store the key-value data.
*
* This implementation creates a new HashEntry instance.
* Subclasses can override this to return a different storage class,
* or implement caching.
*
* @param next the next entry in sequence
* @param hashCode the hash code to use
* @param key the key to store
* @param value the value to store
* @return the newly created entry
*/
protected HashEntry createEntry(final HashEntry next, final int hashCode, final K key, final V value) {
return new HashEntry<>(next, hashCode, convertKey(key), value);
}
/**
* Adds an entry into this map.
*
* This implementation adds the entry to the data storage table.
* Subclasses could override to handle changes to the map.
*
* @param entry the entry to add
* @param hashIndex the index into the data array to store at
*/
protected void addEntry(final HashEntry entry, final int hashIndex) {
data[hashIndex] = entry;
}
//-----------------------------------------------------------------------
/**
* Removes a mapping from the map.
*
* This implementation calls removeEntry() and destroyEntry().
* It also handles changes to modCount and size.
* Subclasses could override to fully control removals from the map.
*
* @param entry the entry to remove
* @param hashIndex the index into the data structure
* @param previous the previous entry in the chain
*/
protected void removeMapping(final HashEntry entry, final int hashIndex, final HashEntry previous) {
modCount++;
removeEntry(entry, hashIndex, previous);
size--;
destroyEntry(entry);
}
/**
* Removes an entry from the chain stored in a particular index.
*
* This implementation removes the entry from the data storage table.
* The size is not updated.
* Subclasses could override to handle changes to the map.
*
* @param entry the entry to remove
* @param hashIndex the index into the data structure
* @param previous the previous entry in the chain
*/
protected void removeEntry(final HashEntry entry, final int hashIndex, final HashEntry previous) {
if (previous == null) {
data[hashIndex] = entry.next;
} else {
previous.next = entry.next;
}
}
/**
* Kills an entry ready for the garbage collector.
*
* This implementation prepares the HashEntry for garbage collection.
* Subclasses can override this to implement caching (override clear as well).
*
* @param entry the entry to destroy
*/
protected void destroyEntry(final HashEntry entry) {
entry.next = null;
entry.key = null;
entry.value = null;
}
//-----------------------------------------------------------------------
/**
* Checks the capacity of the map and enlarges it if necessary.
*
* This implementation uses the threshold to check if the map needs enlarging
*/
protected void checkCapacity() {
if (size >= threshold) {
final int newCapacity = data.length * 2;
if (newCapacity <= MAXIMUM_CAPACITY) {
ensureCapacity(newCapacity);
}
}
}
/**
* Changes the size of the data structure to the capacity proposed.
*
* @param newCapacity the new capacity of the array (a power of two, less or equal to max)
*/
@SuppressWarnings("unchecked")
protected void ensureCapacity(final int newCapacity) {
final int oldCapacity = data.length;
if (newCapacity <= oldCapacity) {
return;
}
if (size == 0) {
threshold = calculateThreshold(newCapacity, loadFactor);
data = new HashEntry[newCapacity];
} else {
final HashEntry oldEntries[] = data;
final HashEntry newEntries[] = new HashEntry[newCapacity];
modCount++;
for (int i = oldCapacity - 1; i >= 0; i--) {
HashEntry entry = oldEntries[i];
if (entry != null) {
oldEntries[i] = null; // gc
do {
final HashEntry next = entry.next;
final int index = hashIndex(entry.hashCode, newCapacity);
entry.next = newEntries[index];
newEntries[index] = entry;
entry = next;
} while (entry != null);
}
}
threshold = calculateThreshold(newCapacity, loadFactor);
data = newEntries;
}
}
/**
* Calculates the new capacity of the map.
* This implementation normalizes the capacity to a power of two.
*
* @param proposedCapacity the proposed capacity
* @return the normalized new capacity
*/
protected int calculateNewCapacity(final int proposedCapacity) {
int newCapacity = 1;
if (proposedCapacity > MAXIMUM_CAPACITY) {
newCapacity = MAXIMUM_CAPACITY;
} else {
while (newCapacity < proposedCapacity) {
newCapacity <<= 1; // multiply by two
}
if (newCapacity > MAXIMUM_CAPACITY) {
newCapacity = MAXIMUM_CAPACITY;
}
}
return newCapacity;
}
/**
* Calculates the new threshold of the map, where it will be resized.
* This implementation uses the load factor.
*
* @param newCapacity the new capacity
* @param factor the load factor
* @return the new resize threshold
*/
protected int calculateThreshold(final int newCapacity, final float factor) {
return (int) (newCapacity * factor);
}
//-----------------------------------------------------------------------
/**
* Gets the next field from a HashEntry.
* Used in subclasses that have no visibility of the field.
*
* @param entry the entry to query, must not be null
* @return the next field of the entry
* @throws NullPointerException if the entry is null
* @since 3.1
*/
protected HashEntry entryNext(final HashEntry entry) {
return entry.next;
}
/**
* Gets the hashCode field from a HashEntry.
* Used in subclasses that have no visibility of the field.
*
* @param entry the entry to query, must not be null
* @return the hashCode field of the entry
* @throws NullPointerException if the entry is null
* @since 3.1
*/
protected int entryHashCode(final HashEntry entry) {
return entry.hashCode;
}
/**
* Gets the key field from a HashEntry.
* Used in subclasses that have no visibility of the field.
*
* @param entry the entry to query, must not be null
* @return the key field of the entry
* @throws NullPointerException if the entry is null
* @since 3.1
*/
protected K entryKey(final HashEntry entry) {
return entry.getKey();
}
/**
* Gets the value field from a HashEntry.
* Used in subclasses that have no visibility of the field.
*
* @param entry the entry to query, must not be null
* @return the value field of the entry
* @throws NullPointerException if the entry is null
* @since 3.1
*/
protected V entryValue(final HashEntry entry) {
return entry.getValue();
}
//-----------------------------------------------------------------------
/**
* Gets an iterator over the map.
* Changes made to the iterator affect this map.
*
* A MapIterator returns the keys in the map. It also provides convenient
* methods to get the key and value, and set the value.
* It avoids the need to create an entrySet/keySet/values object.
* It also avoids creating the Map.Entry object.
*
* @return the map iterator
*/
@Override
public MapIterator mapIterator() {
if (size == 0) {
return EmptyMapIterator.emptyMapIterator();
}
return new HashMapIterator<>(this);
}
/**
* MapIterator implementation.
*/
protected static class HashMapIterator extends HashIterator implements MapIterator {
protected HashMapIterator(final AbstractHashedMap parent) {
super(parent);
}
@Override
public K next() {
return super.nextEntry().getKey();
}
@Override
public K getKey() {
final HashEntry current = currentEntry();
if (current == null) {
throw new IllegalStateException(AbstractHashedMap.GETKEY_INVALID);
}
return current.getKey();
}
@Override
public V getValue() {
final HashEntry current = currentEntry();
if (current == null) {
throw new IllegalStateException(AbstractHashedMap.GETVALUE_INVALID);
}
return current.getValue();
}
@Override
public V setValue(final V value) {
final HashEntry current = currentEntry();
if (current == null) {
throw new IllegalStateException(AbstractHashedMap.SETVALUE_INVALID);
}
return current.setValue(value);
}
}
//-----------------------------------------------------------------------
/**
* Gets the entrySet view of the map.
* Changes made to the view affect this map.
* To simply iterate through the entries, use {@link #mapIterator()}.
*
* @return the entrySet view
*/
@Override
public Set> entrySet() {
if (entrySet == null) {
entrySet = new EntrySet<>(this);
}
return entrySet;
}
/**
* Creates an entry set iterator.
* Subclasses can override this to return iterators with different properties.
*
* @return the entrySet iterator
*/
protected Iterator> createEntrySetIterator() {
if (size() == 0) {
return EmptyIterator.>emptyIterator();
}
return new EntrySetIterator<>(this);
}
/**
* EntrySet implementation.
*/
protected static class EntrySet extends AbstractSet> {
/** The parent map */
private final AbstractHashedMap parent;
protected EntrySet(final AbstractHashedMap parent) {
super();
this.parent = parent;
}
@Override
public int size() {
return parent.size();
}
@Override
public void clear() {
parent.clear();
}
@Override
public boolean contains(final Object entry) {
if (entry instanceof Map.Entry) {
final Map.Entry e = (Map.Entry) entry;
final Entry match = parent.getEntry(e.getKey());
return match != null && match.equals(e);
}
return false;
}
@Override
public boolean remove(final Object obj) {
if (obj instanceof Map.Entry == false) {
return false;
}
if (contains(obj) == false) {
return false;
}
final Map.Entry entry = (Map.Entry) obj;
parent.remove(entry.getKey());
return true;
}
@Override
public Iterator> iterator() {
return parent.createEntrySetIterator();
}
}
/**
* EntrySet iterator.
*/
protected static class EntrySetIterator extends HashIterator implements Iterator> {
protected EntrySetIterator(final AbstractHashedMap parent) {
super(parent);
}
@Override
public Map.Entry next() {
return super.nextEntry();
}
}
//-----------------------------------------------------------------------
/**
* Gets the keySet view of the map.
* Changes made to the view affect this map.
* To simply iterate through the keys, use {@link #mapIterator()}.
*
* @return the keySet view
*/
@Override
public Set keySet() {
if (keySet == null) {
keySet = new KeySet<>(this);
}
return keySet;
}
/**
* Creates a key set iterator.
* Subclasses can override this to return iterators with different properties.
*
* @return the keySet iterator
*/
protected Iterator createKeySetIterator() {
if (size() == 0) {
return EmptyIterator.emptyIterator();
}
return new KeySetIterator<>(this);
}
/**
* KeySet implementation.
*/
protected static class KeySet extends AbstractSet {
/** The parent map */
private final AbstractHashedMap parent;
protected KeySet(final AbstractHashedMap parent) {
super();
this.parent = parent;
}
@Override
public int size() {
return parent.size();
}
@Override
public void clear() {
parent.clear();
}
@Override
public boolean contains(final Object key) {
return parent.containsKey(key);
}
@Override
public boolean remove(final Object key) {
final boolean result = parent.containsKey(key);
parent.remove(key);
return result;
}
@Override
public Iterator iterator() {
return parent.createKeySetIterator();
}
}
/**
* KeySet iterator.
*/
protected static class KeySetIterator extends HashIterator implements Iterator {
@SuppressWarnings("unchecked")
protected KeySetIterator(final AbstractHashedMap parent) {
super((AbstractHashedMap) parent);
}
@Override
public K next() {
return super.nextEntry().getKey();
}
}
//-----------------------------------------------------------------------
/**
* Gets the values view of the map.
* Changes made to the view affect this map.
* To simply iterate through the values, use {@link #mapIterator()}.
*
* @return the values view
*/
@Override
public Collection values() {
if (values == null) {
values = new Values<>(this);
}
return values;
}
/**
* Creates a values iterator.
* Subclasses can override this to return iterators with different properties.
*
* @return the values iterator
*/
protected Iterator createValuesIterator() {
if (size() == 0) {
return EmptyIterator.emptyIterator();
}
return new ValuesIterator<>(this);
}
/**
* Values implementation.
*/
protected static class Values extends AbstractCollection {
/** The parent map */
private final AbstractHashedMap parent;
protected Values(final AbstractHashedMap parent) {
super();
this.parent = parent;
}
@Override
public int size() {
return parent.size();
}
@Override
public void clear() {
parent.clear();
}
@Override
public boolean contains(final Object value) {
return parent.containsValue(value);
}
@Override
public Iterator iterator() {
return parent.createValuesIterator();
}
}
/**
* Values iterator.
*/
protected static class ValuesIterator extends HashIterator implements Iterator {
@SuppressWarnings("unchecked")
protected ValuesIterator(final AbstractHashedMap parent) {
super((AbstractHashedMap) parent);
}
@Override
public V next() {
return super.nextEntry().getValue();
}
}
//-----------------------------------------------------------------------
/**
* HashEntry used to store the data.
*
* If you subclass AbstractHashedMap but not HashEntry
* then you will not be able to access the protected fields.
* The entryXxx() methods on AbstractHashedMap exist
* to provide the necessary access.
*/
protected static class HashEntry implements Map.Entry, KeyValue {
/** The next entry in the hash chain */
protected HashEntry next;
/** The hash code of the key */
protected int hashCode;
/** The key */
protected Object key;
/** The value */
protected Object value;
protected HashEntry(final HashEntry next, final int hashCode, final Object key, final V value) {
super();
this.next = next;
this.hashCode = hashCode;
this.key = key;
this.value = value;
}
@Override
@SuppressWarnings("unchecked")
public K getKey() {
if (key == NULL) {
return null;
}
return (K) key;
}
@Override
@SuppressWarnings("unchecked")
public V getValue() {
return (V) value;
}
@Override
@SuppressWarnings("unchecked")
public V setValue(final V value) {
final Object old = this.value;
this.value = value;
return (V) old;
}
@Override
public boolean equals(final Object obj) {
if (obj == this) {
return true;
}
if (obj instanceof Map.Entry == false) {
return false;
}
final Map.Entry other = (Map.Entry) obj;
return
(getKey() == null ? other.getKey() == null : getKey().equals(other.getKey())) &&
(getValue() == null ? other.getValue() == null : getValue().equals(other.getValue()));
}
@Override
public int hashCode() {
return (getKey() == null ? 0 : getKey().hashCode()) ^
(getValue() == null ? 0 : getValue().hashCode());
}
@Override
public String toString() {
return new StringBuilder().append(getKey()).append('=').append(getValue()).toString();
}
}
/**
* Base Iterator
*/
protected static abstract class HashIterator {
/** The parent map */
private final AbstractHashedMap parent;
/** The current index into the array of buckets */
private int hashIndex;
/** The last returned entry */
private HashEntry last;
/** The next entry */
private HashEntry next;
/** The modification count expected */
private int expectedModCount;
protected HashIterator(final AbstractHashedMap parent) {
super();
this.parent = parent;
final HashEntry[] data = parent.data;
int i = data.length;
HashEntry next = null;
while (i > 0 && next == null) {
next = data[--i];
}
this.next = next;
this.hashIndex = i;
this.expectedModCount = parent.modCount;
}
public boolean hasNext() {
return next != null;
}
protected HashEntry nextEntry() {
if (parent.modCount != expectedModCount) {
throw new ConcurrentModificationException();
}
final HashEntry newCurrent = next;
if (newCurrent == null) {
throw new NoSuchElementException(AbstractHashedMap.NO_NEXT_ENTRY);
}
final HashEntry[] data = parent.data;
int i = hashIndex;
HashEntry n = newCurrent.next;
while (n == null && i > 0) {
n = data[--i];
}
next = n;
hashIndex = i;
last = newCurrent;
return newCurrent;
}
protected HashEntry currentEntry() {
return last;
}
public void remove() {
if (last == null) {
throw new IllegalStateException(AbstractHashedMap.REMOVE_INVALID);
}
if (parent.modCount != expectedModCount) {
throw new ConcurrentModificationException();
}
parent.remove(last.getKey());
last = null;
expectedModCount = parent.modCount;
}
@Override
public String toString() {
if (last != null) {
return "Iterator[" + last.getKey() + "=" + last.getValue() + "]";
}
return "Iterator[]";
}
}
//-----------------------------------------------------------------------
/**
* Writes the map data to the stream. This method must be overridden if a
* subclass must be setup before put() is used.
*
* Serialization is not one of the JDK's nicest topics. Normal serialization will
* initialise the superclass before the subclass. Sometimes however, this isn't
* what you want, as in this case the put() method on read can be
* affected by subclass state.
*
* The solution adopted here is to serialize the state data of this class in
* this protected method. This method must be called by the
* writeObject() of the first serializable subclass.
*
* Subclasses may override if they have a specific field that must be present
* on read before this implementation will work. Generally, the read determines
* what must be serialized here, if anything.
*
* @param out the output stream
* @throws IOException if an error occurs while writing tothe stream
*/
protected void doWriteObject(final ObjectOutputStream out) throws IOException {
out.writeFloat(loadFactor);
out.writeInt(data.length);
out.writeInt(size);
for (final MapIterator it = mapIterator(); it.hasNext();) {
out.writeObject(it.next());
out.writeObject(it.getValue());
}
}
/**
* Reads the map data from the stream. This method must be overridden if a
* subclass must be setup before put() is used.
*
* Serialization is not one of the JDK's nicest topics. Normal serialization will
* initialise the superclass before the subclass. Sometimes however, this isn't
* what you want, as in this case the put() method on read can be
* affected by subclass state.
*
* The solution adopted here is to deserialize the state data of this class in
* this protected method. This method must be called by the
* readObject() of the first serializable subclass.
*
* Subclasses may override if the subclass has a specific field that must be present
* before put() or calculateThreshold() will work correctly.
*
* @param in the input stream
* @throws IOException if an error occurs while reading from the stream
* @throws ClassNotFoundException if an object read from the stream can not be loaded
*/
@SuppressWarnings("unchecked")
protected void doReadObject(final ObjectInputStream in) throws IOException, ClassNotFoundException {
loadFactor = in.readFloat();
final int capacity = in.readInt();
final int size = in.readInt();
init();
threshold = calculateThreshold(capacity, loadFactor);
data = new HashEntry[capacity];
for (int i = 0; i < size; i++) {
final K key = (K) in.readObject();
final V value = (V) in.readObject();
put(key, value);
}
}
//-----------------------------------------------------------------------
/**
* Clones the map without cloning the keys or values.
*
* To implement clone(), a subclass must implement the
* Cloneable interface and make this method public.
*
* @return a shallow clone
* @throws InternalError if {@link AbstractMap#clone()} failed
*/
@Override
@SuppressWarnings("unchecked")
protected AbstractHashedMap clone() {
try {
final AbstractHashedMap cloned = (AbstractHashedMap) super.clone();
cloned.data = new HashEntry[data.length];
cloned.entrySet = null;
cloned.keySet = null;
cloned.values = null;
cloned.modCount = 0;
cloned.size = 0;
cloned.init();
cloned.putAll(this);
return cloned;
} catch (final CloneNotSupportedException ex) {
throw new InternalError();
}
}
/**
* Compares this map with another.
*
* @param obj the object to compare to
* @return true if equal
*/
@Override
public boolean equals(final Object obj) {
if (obj == this) {
return true;
}
if (obj instanceof Map == false) {
return false;
}
final Map map = (Map) obj;
if (map.size() != size()) {
return false;
}
final MapIterator it = mapIterator();
try {
while (it.hasNext()) {
final Object key = it.next();
final Object value = it.getValue();
if (value == null) {
if (map.get(key) != null || map.containsKey(key) == false) {
return false;
}
} else {
if (value.equals(map.get(key)) == false) {
return false;
}
}
}
} catch (final ClassCastException ignored) {
return false;
} catch (final NullPointerException ignored) {
return false;
}
return true;
}
/**
* Gets the standard Map hashCode.
*
* @return the hash code defined in the Map interface
*/
@Override
public int hashCode() {
int total = 0;
final Iterator> it = createEntrySetIterator();
while (it.hasNext()) {
total += it.next().hashCode();
}
return total;
}
/**
* Gets the map as a String.
*
* @return a string version of the map
*/
@Override
public String toString() {
if (size() == 0) {
return "{}";
}
final StringBuilder buf = new StringBuilder(32 * size());
buf.append('{');
final MapIterator it = mapIterator();
boolean hasNext = it.hasNext();
while (hasNext) {
final K key = it.next();
final V value = it.getValue();
buf.append(key == this ? "(this Map)" : key)
.append('=')
.append(value == this ? "(this Map)" : value);
hasNext = it.hasNext();
if (hasNext) {
buf.append(',').append(' ');
}
}
buf.append('}');
return buf.toString();
}
}