KeyComparatorLinkedHashMap.java
/*
* Copyright (c) 2010, 2018 Oracle and/or its affiliates. All rights reserved.
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v. 2.0, which is available at
* http://www.eclipse.org/legal/epl-2.0.
*
* This Source Code may also be made available under the following Secondary
* Licenses when the conditions for such availability set forth in the
* Eclipse Public License v. 2.0 are satisfied: GNU General Public License,
* version 2 with the GNU Classpath Exception, which is available at
* https://www.gnu.org/software/classpath/license.html.
*
* SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
*/
package org.glassfish.jersey.internal.util.collection;
import java.util.ConcurrentModificationException;
import java.util.Iterator;
import java.util.Map;
import java.util.NoSuchElementException;
/**
* A implementation similar to {@link java.util.LinkedHashMap} but supports the
* comparison of keys using a {@link KeyComparator}.
*
* @param <K> Type of keys
* @param <V> Type of values
* @author Paul Sandoz
*/
public class KeyComparatorLinkedHashMap<K, V>
extends KeyComparatorHashMap<K, V>
implements Map<K, V> {
private static final long serialVersionUID = 3801124242820219131L;
/**
* The head of the doubly linked list.
*/
private transient Entry<K, V> header;
/**
* The iteration ordering method for this linked hash map: <tt>true</tt>
* for access-order, <tt>false</tt> for insertion-order.
*
* @serial
*/
private final boolean accessOrder;
/**
* Constructs an empty insertion-ordered <tt>LinkedHashMap</tt> instance
* with the specified initial capacity and load factor.
*
* @param initialCapacity the initial capacity
* @param loadFactor the load factor
* @param keyComparator the comparator
* @throws IllegalArgumentException if the initial capacity is negative
* or the load factor is nonpositive
*/
public KeyComparatorLinkedHashMap(int initialCapacity, float loadFactor,
KeyComparator<K> keyComparator) {
super(initialCapacity, loadFactor, keyComparator);
accessOrder = false;
}
/**
* Constructs an empty insertion-ordered <tt>LinkedHashMap</tt> instance
* with the specified initial capacity and a default load factor (0.75).
*
* @param initialCapacity the initial capacity
* @param keyComparator the comparator
* @throws IllegalArgumentException if the initial capacity is negative
*/
public KeyComparatorLinkedHashMap(int initialCapacity,
KeyComparator<K> keyComparator) {
super(initialCapacity, keyComparator);
accessOrder = false;
}
/**
* Constructs an empty insertion-ordered <tt>LinkedHashMap</tt> instance
* with the default initial capacity (16) and load factor (0.75).
* @param keyComparator the comparator
*/
public KeyComparatorLinkedHashMap(KeyComparator<K> keyComparator) {
super(keyComparator);
accessOrder = false;
}
/**
* Constructs an insertion-ordered <tt>LinkedHashMap</tt> instance with
* the same mappings as the specified map. The <tt>LinkedHashMap</tt>
* instance is created with a default load factor (0.75) and an initial
* capacity sufficient to hold the mappings in the specified map.
*
* @param m the map whose mappings are to be placed in this map
* @param keyComparator the comparator
* @throws NullPointerException if the specified map is null
*/
public KeyComparatorLinkedHashMap(Map<? extends K, ? extends V> m,
KeyComparator<K> keyComparator) {
super(m, keyComparator);
accessOrder = false;
}
/**
* Constructs an empty <tt>LinkedHashMap</tt> instance with the
* specified initial capacity, load factor and ordering mode.
*
* @param initialCapacity the initial capacity
* @param loadFactor the load factor
* @param accessOrder the ordering mode - <tt>true</tt> for
* access-order, <tt>false</tt> for insertion-order
* @param keyComparator the comparator
* @throws IllegalArgumentException if the initial capacity is negative
* or the load factor is nonpositive
*/
public KeyComparatorLinkedHashMap(int initialCapacity,
float loadFactor,
boolean accessOrder, KeyComparator<K> keyComparator) {
super(initialCapacity, loadFactor, keyComparator);
this.accessOrder = accessOrder;
}
/**
* Called by superclass constructors and pseudoconstructors (clone,
* readObject) before any entries are inserted into the map. Initializes
* the chain.
*/
@Override
void init() {
header = new Entry<K, V>(-1, null, null, null);
header.before = header.after = header;
}
/**
* Transfers all entries to new table array. This method is called
* by superclass resize. It is overridden for performance, as it is
* faster to iterate using our linked list.
*/
@Override
@SuppressWarnings("unchecked")
void transfer(KeyComparatorHashMap.Entry[] newTable) {
int newCapacity = newTable.length;
for (Entry<K, V> e = header.after; e != header; e = e.after) {
int index = indexFor(e.hash, newCapacity);
e.next = newTable[index];
newTable[index] = e;
}
}
/**
* 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
*/
@Override
public boolean containsValue(Object value) {
// Overridden to take advantage of faster iterator
if (value == null) {
for (Entry e = header.after; e != header; e = e.after) {
if (e.value == null) {
return true;
}
}
} else {
for (Entry e = header.after; e != header; e = e.after) {
if (value.equals(e.value)) {
return true;
}
}
}
return false;
}
/**
* Returns the value to which the specified key is mapped,
* or {@code null} if this map contains no mapping for the key.
*
* <p>More formally, if this map contains a mapping from a key
* {@code k} to a value {@code v} such that {@code (key==null ? k==null :
* key.equals(k))}, then this method returns {@code v}; otherwise
* it returns {@code null}. (There can be at most one such mapping.)
*
* <p>A return value of {@code null} does not <i>necessarily</i>
* indicate that the map contains no mapping for the key; it's also
* possible that the map explicitly maps the key to {@code null}.
* The {@link #containsKey containsKey} operation may be used to
* distinguish these two cases.
*/
@Override
public V get(Object key) {
@SuppressWarnings("unchecked")
Entry<K, V> e = (Entry<K, V>) getEntry((K) key);
if (e == null) {
return null;
}
e.recordAccess(this);
return e.value;
}
/**
* Removes all of the mappings from this map.
* The map will be empty after this call returns.
*/
@Override
public void clear() {
super.clear();
header.before = header.after = header;
}
/**
* LinkedHashMap entry.
*/
private static class Entry<K, V> extends KeyComparatorHashMap.Entry<K, V> {
// These fields comprise the doubly linked list used for iteration.
Entry<K, V> before, after;
Entry(int hash, K key, V value, KeyComparatorHashMap.Entry<K, V> next) {
super(hash, key, value, next);
}
/**
* Removes this entry from the linked list.
*/
private void remove() {
before.after = after;
after.before = before;
}
/**
* Inserts this entry before the specified existing entry in the list.
*/
private void addBefore(Entry<K, V> existingEntry) {
after = existingEntry;
before = existingEntry.before;
before.after = this;
after.before = this;
}
/**
* This method is invoked by the superclass whenever the value
* of a pre-existing entry is read by Map.get or modified by Map.set.
* If the enclosing Map is access-ordered, it moves the entry
* to the end of the list; otherwise, it does nothing.
*/
@Override
void recordAccess(KeyComparatorHashMap<K, V> m) {
KeyComparatorLinkedHashMap<K, V> lm = (KeyComparatorLinkedHashMap<K, V>) m;
if (lm.accessOrder) {
lm.modCount++;
remove();
addBefore(lm.header);
}
}
@Override
void recordRemoval(KeyComparatorHashMap<K, V> m) {
remove();
}
@Override
public boolean equals(Object obj) {
return super.equals(obj);
}
@Override
public int hashCode() {
return super.hashCode();
}
}
private abstract class LinkedHashIterator<T> implements Iterator<T> {
Entry<K, V> nextEntry = header.after;
Entry<K, V> lastReturned = null;
/**
* The modCount value that the iterator believes that the backing
* List should have. If this expectation is violated, the iterator
* has detected concurrent modification.
*/
int expectedModCount = modCount;
@Override
public boolean hasNext() {
return nextEntry != header;
}
@Override
public void remove() {
if (lastReturned == null) {
throw new IllegalStateException();
}
if (modCount != expectedModCount) {
throw new ConcurrentModificationException();
}
KeyComparatorLinkedHashMap.this.remove(lastReturned.key);
lastReturned = null;
expectedModCount = modCount;
}
Entry<K, V> nextEntry() {
if (modCount != expectedModCount) {
throw new ConcurrentModificationException();
}
if (nextEntry == header) {
throw new NoSuchElementException();
}
Entry<K, V> e = lastReturned = nextEntry;
nextEntry = e.after;
return e;
}
}
private class KeyIterator extends LinkedHashIterator<K> {
@Override
public K next() {
return nextEntry().getKey();
}
}
private class ValueIterator extends LinkedHashIterator<V> {
@Override
public V next() {
return nextEntry().value;
}
}
private class EntryIterator extends LinkedHashIterator<Map.Entry<K, V>> {
@Override
public Map.Entry<K, V> next() {
return nextEntry();
}
}
// These Overrides alter the behavior of superclass view iterator() methods
@Override
Iterator<K> newKeyIterator() {
return new KeyIterator();
}
@Override
Iterator<V> newValueIterator() {
return new ValueIterator();
}
@Override
Iterator<Map.Entry<K, V>> newEntryIterator() {
return new EntryIterator();
}
/**
* This override alters behavior of superclass put method. It causes newly
* allocated entry to get inserted at the end of the linked list and
* removes the eldest entry if appropriate.
*/
@Override
void addEntry(int hash, K key, V value, int bucketIndex) {
createEntry(hash, key, value, bucketIndex);
// Remove eldest entry if instructed, else grow capacity if appropriate
Entry<K, V> eldest = header.after;
if (removeEldestEntry(eldest)) {
removeEntryForKey(eldest.key);
} else {
if (size >= threshold) {
resize(2 * table.length);
}
}
}
/**
* This override differs from addEntry in that it doesn't resize the
* table or remove the eldest entry.
*/
@Override
void createEntry(int hash, K key, V value, int bucketIndex) {
KeyComparatorHashMap.Entry<K, V> old = table[bucketIndex];
Entry<K, V> e = new Entry<K, V>(hash, key, value, old);
table[bucketIndex] = e;
e.addBefore(header);
size++;
}
/**
* Returns <tt>true</tt> if this map should remove its eldest entry.
* This method is invoked by <tt>put</tt> and <tt>putAll</tt> after
* inserting a new entry into the map. It provides the implementor
* with the opportunity to remove the eldest entry each time a new one
* is added. This is useful if the map represents a cache: it allows
* the map to reduce memory consumption by deleting stale entries.
*
* <p>Sample use: this override will allow the map to grow up to 100
* entries and then delete the eldest entry each time a new entry is
* added, maintaining a steady state of 100 entries.
* <pre>
* private static final int MAX_ENTRIES = 100;
*
* protected boolean removeEldestEntry(Map.Entry eldest) {
* return size() > MAX_ENTRIES;
* }
* </pre>
*
* <p>This method typically does not modify the map in any way,
* instead allowing the map to modify itself as directed by its
* return value. It <i>is</i> permitted for this method to modify
* the map directly, but if it does so, it <i>must</i> return
* <tt>false</tt> (indicating that the map should not attempt any
* further modification). The effects of returning <tt>true</tt>
* after modifying the map from within this method are unspecified.
*
* <p>This implementation merely returns <tt>false</tt> (so that this
* map acts like a normal map - the eldest element is never removed).
*
* @param eldest The least recently inserted entry in the map, or if
* this is an access-ordered map, the least recently accessed
* entry. This is the entry that will be removed it this
* method returns <tt>true</tt>. If the map was empty prior
* to the <tt>put</tt> or <tt>putAll</tt> invocation resulting
* in this invocation, this will be the entry that was just
* inserted; in other words, if the map contains a single
* entry, the eldest entry is also the newest.
* @return <tt>true</tt> if the eldest entry should be removed
* from the map; <tt>false</tt> if it should be retained.
*/
protected boolean removeEldestEntry(Map.Entry<K, V> eldest) {
return false;
}
}