/*
 * Copyright (c) 1997, 2018, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
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 */

package java.util;

import java.util.function.Consumer;
import java.util.function.BiConsumer;
import java.util.function.BiFunction;
import java.io.IOException;

/**
 * <p>Hash table and linked list implementation of the {@code Map} interface,
 * with predictable iteration order. This implementation differs from
 * {@code HashMap} in that it maintains a doubly-linked list running through
 * all of its entries. This linked list defines the iteration ordering,
 * which is normally the order in which keys were inserted into the map
 * (<i>insertion-order</i>). Note that insertion order is not affected
 * if a key is <i>re-inserted</i> into the map. (A key {@code k} is
 * reinserted into a map {@code m} if {@code m.put(k, v)} is invoked when
 * {@code m.containsKey(k)} would return {@code true} immediately prior to
 * the invocation.)
 *
 * <p>This implementation spares its clients from the unspecified, generally
 * chaotic ordering provided by {@link HashMap} (and {@link Hashtable}),
 * without incurring the increased cost associated with {@link TreeMap}. It
 * can be used to produce a copy of a map that has the same order as the
 * original, regardless of the original map's implementation:
 * <pre>
 * void foo(Map m) {
 * Map copy = new LinkedHashMap(m);
 * ...
 * }
 * </pre>
 * This technique is particularly useful if a module takes a map on input,
 * copies it, and later returns results whose order is determined by that of
 * the copy. (Clients generally appreciate having things returned in the same
 * order they were presented.)
 *
 * <p>A special {@link #LinkedHashMap(int,float,boolean) constructor} is
 * provided to create a linked hash map whose order of iteration is the order
 * in which its entries were last accessed, from least-recently accessed to
 * most-recently (<i>access-order</i>). This kind of map is well-suited to
 * building LRU caches. Invoking the {@code put}, {@code putIfAbsent},
 * {@code get}, {@code getOrDefault}, {@code compute}, {@code computeIfAbsent},
 * {@code computeIfPresent}, or {@code merge} methods results
 * in an access to the corresponding entry (assuming it exists after the
 * invocation completes). The {@code replace} methods only result in an access
 * of the entry if the value is replaced. The {@code putAll} method generates one
 * entry access for each mapping in the specified map, in the order that
 * key-value mappings are provided by the specified map's entry set iterator.
 * <i>No other methods generate entry accesses.</i> In particular, operations
 * on collection-views do <i>not</i> affect the order of iteration of the
 * backing map.
 *
 * <p>The {@link #removeEldestEntry(Map.Entry)} method may be overridden to
 * impose a policy for removing stale mappings automatically when new mappings
 * are added to the map.
 *
 * <p>This class provides all of the optional {@code Map} operations, and
 * permits null elements. Like {@code HashMap}, it provides constant-time
 * performance for the basic operations ({@code add}, {@code contains} and
 * {@code remove}), assuming the hash function disperses elements
 * properly among the buckets. Performance is likely to be just slightly
 * below that of {@code HashMap}, due to the added expense of maintaining the
 * linked list, with one exception: Iteration over the collection-views
 * of a {@code LinkedHashMap} requires time proportional to the <i>size</i>
 * of the map, regardless of its capacity. Iteration over a {@code HashMap}
 * is likely to be more expensive, requiring time proportional to its
 * <i>capacity</i>.
 *
 * <p>A linked hash map has two parameters that affect its performance:
 * <i>initial capacity</i> and <i>load factor</i>. They are defined precisely
 * as for {@code HashMap}. Note, however, that the penalty for choosing an
 * excessively high value for initial capacity is less severe for this class
 * than for {@code HashMap}, as iteration times for this class are unaffected
 * by capacity.
 *
 * <p><strong>Note that this implementation is not synchronized.</strong>
 * If multiple threads access a linked hash map concurrently, and at least
 * one of the threads modifies the map structurally, it <em>must</em> be
 * synchronized externally. This is typically accomplished by
 * synchronizing on some object that naturally encapsulates the map.
 *
 * If no such object exists, the map should be "wrapped" using the
 * {@link Collections#synchronizedMap Collections.synchronizedMap}
 * method. This is best done at creation time, to prevent accidental
 * unsynchronized access to the map:<pre>
 * Map m = Collections.synchronizedMap(new LinkedHashMap(...));</pre>
 *
 * A structural modification is any operation that adds or deletes one or more
 * mappings or, in the case of access-ordered linked hash maps, affects
 * iteration order. In insertion-ordered linked hash maps, merely changing
 * the value associated with a key that is already contained in the map is not
 * a structural modification. <strong>In access-ordered linked hash maps,
 * merely querying the map with {@code get} is a structural modification.
 * </strong>)
 *
 * <p>The iterators returned by the {@code iterator} method of the collections
 * returned by all of this class's collection view methods are
 * <em>fail-fast</em>: if the map is structurally modified at any time after
 * the iterator is created, in any way except through the iterator's own
 * {@code remove} method, the iterator will throw a {@link
 * ConcurrentModificationException}. Thus, in the face of concurrent
 * modification, the iterator fails quickly and cleanly, rather than risking
 * arbitrary, non-deterministic behavior at an undetermined time in the future.
 *
 * <p>Note that the fail-fast behavior of an iterator cannot be guaranteed
 * as it is, generally speaking, impossible to make any hard guarantees in the
 * presence of unsynchronized concurrent modification. Fail-fast iterators
 * throw {@code ConcurrentModificationException} on a best-effort basis.
 * Therefore, it would be wrong to write a program that depended on this
 * exception for its correctness: <i>the fail-fast behavior of iterators
 * should be used only to detect bugs.</i>
 *
 * <p>The spliterators returned by the spliterator method of the collections
 * returned by all of this class's collection view methods are
 * <em><a href="Spliterator.html#binding">late-binding</a></em>,
 * <em>fail-fast</em>, and additionally report {@link Spliterator#ORDERED}.
 *
 * <p>This class is a member of the
 * <a href="{@docRoot}/java.base/java/util/package-summary.html#CollectionsFramework">
 * Java Collections Framework</a>.
 *
 * @implNote
 * The spliterators returned by the spliterator method of the collections
 * returned by all of this class's collection view methods are created from
 * the iterators of the corresponding collections.
 *
 * @param <K> the type of keys maintained by this map
 * @param <V> the type of mapped values
 *
 * @author Josh Bloch
 * @see Object#hashCode()
 * @see Collection
 * @see Map
 * @see HashMap
 * @see TreeMap
 * @see Hashtable
 * @since 1.4
 */
public class LinkedHashMap<K,V>
 extends HashMap<K,V>
 implements Map<K,V>
{

 /*
 * Implementation note. A previous version of this class was
 * internally structured a little differently. Because superclass
 * HashMap now uses trees for some of its nodes, class
 * LinkedHashMap.Entry is now treated as intermediary node class
 * that can also be converted to tree form. The name of this
 * class, LinkedHashMap.Entry, is confusing in several ways in its
 * current context, but cannot be changed. Otherwise, even though
 * it is not exported outside this package, some existing source
 * code is known to have relied on a symbol resolution corner case
 * rule in calls to removeEldestEntry that suppressed compilation
 * errors due to ambiguous usages. So, we keep the name to
 * preserve unmodified compilability.
 *
 * The changes in node classes also require using two fields
 * (head, tail) rather than a pointer to a header node to maintain
 * the doubly-linked before/after list. This class also
 * previously used a different style of callback methods upon
 * access, insertion, and removal.
 */

 /**
 * HashMap.Node subclass for normal LinkedHashMap entries.
 */
 static class Entry<K,V> extends HashMap.Node<K,V> {
 Entry<K,V> before, after;
 Entry(int hash, K key, V value, Node<K,V> next) {
 super(hash, key, value, next);
 }
 }

 private static final long serialVersionUID = 3801124242820219131L;

 /**
 * The head (eldest) of the doubly linked list.
 */
 transient LinkedHashMap.Entry<K,V> head;

 /**
 * The tail (youngest) of the doubly linked list.
 */
 transient LinkedHashMap.Entry<K,V> tail;

 /**
 * The iteration ordering method for this linked hash map: {@code true}
 * for access-order, {@code false} for insertion-order.
 *
 * @serial
 */
 final boolean accessOrder;

 // internal utilities

 // link at the end of list
 private void linkNodeLast(LinkedHashMap.Entry<K,V> p) {
 LinkedHashMap.Entry<K,V> last = tail;
 tail = p;
 if (last == null)
 head = p;
 else {
 p.before = last;
 last.after = p;
 }
 }

 // apply src's links to dst
 private void transferLinks(LinkedHashMap.Entry<K,V> src,
 LinkedHashMap.Entry<K,V> dst) {
 LinkedHashMap.Entry<K,V> b = dst.before = src.before;
 LinkedHashMap.Entry<K,V> a = dst.after = src.after;
 if (b == null)
 head = dst;
 else
 b.after = dst;
 if (a == null)
 tail = dst;
 else
 a.before = dst;
 }

 // overrides of HashMap hook methods

 void reinitialize() {
 super.reinitialize();
 head = tail = null;
 }

 Node<K,V> newNode(int hash, K key, V value, Node<K,V> e) {
 LinkedHashMap.Entry<K,V> p =
 new LinkedHashMap.Entry<>(hash, key, value, e);
 linkNodeLast(p);
 return p;
 }

 Node<K,V> replacementNode(Node<K,V> p, Node<K,V> next) {
 LinkedHashMap.Entry<K,V> q = (LinkedHashMap.Entry<K,V>)p;
 LinkedHashMap.Entry<K,V> t =
 new LinkedHashMap.Entry<>(q.hash, q.key, q.value, next);
 transferLinks(q, t);
 return t;
 }

 TreeNode<K,V> newTreeNode(int hash, K key, V value, Node<K,V> next) {
 TreeNode<K,V> p = new TreeNode<>(hash, key, value, next);
 linkNodeLast(p);
 return p;
 }

 TreeNode<K,V> replacementTreeNode(Node<K,V> p, Node<K,V> next) {
 LinkedHashMap.Entry<K,V> q = (LinkedHashMap.Entry<K,V>)p;
 TreeNode<K,V> t = new TreeNode<>(q.hash, q.key, q.value, next);
 transferLinks(q, t);
 return t;
 }

 void afterNodeRemoval(Node<K,V> e) { // unlink
 LinkedHashMap.Entry<K,V> p =
 (LinkedHashMap.Entry<K,V>)e, b = p.before, a = p.after;
 p.before = p.after = null;
 if (b == null)
 head = a;
 else
 b.after = a;
 if (a == null)
 tail = b;
 else
 a.before = b;
 }

 void afterNodeInsertion(boolean evict) { // possibly remove eldest
 LinkedHashMap.Entry<K,V> first;
 if (evict && (first = head) != null && removeEldestEntry(first)) {
 K key = first.key;
 removeNode(hash(key), key, null, false, true);
 }
 }

 void afterNodeAccess(Node<K,V> e) { // move node to last
 LinkedHashMap.Entry<K,V> last;
 if (accessOrder && (last = tail) != e) {
 LinkedHashMap.Entry<K,V> p =
 (LinkedHashMap.Entry<K,V>)e, b = p.before, a = p.after;
 p.after = null;
 if (b == null)
 head = a;
 else
 b.after = a;
 if (a != null)
 a.before = b;
 else
 last = b;
 if (last == null)
 head = p;
 else {
 p.before = last;
 last.after = p;
 }
 tail = p;
 ++modCount;
 }
 }

 void internalWriteEntries(java.io.ObjectOutputStream s) throws IOException {
 for (LinkedHashMap.Entry<K,V> e = head; e != null; e = e.after) {
 s.writeObject(e.key);
 s.writeObject(e.value);
 }
 }

 /**
 * Constructs an empty insertion-ordered {@code LinkedHashMap} instance
 * 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 LinkedHashMap(int initialCapacity, float loadFactor) {
 super(initialCapacity, loadFactor);
 accessOrder = false;
 }

 /**
 * Constructs an empty insertion-ordered {@code LinkedHashMap} instance
 * with the specified initial capacity and a default load factor (0.75).
 *
 * @param initialCapacity the initial capacity
 * @throws IllegalArgumentException if the initial capacity is negative
 */
 public LinkedHashMap(int initialCapacity) {
 super(initialCapacity);
 accessOrder = false;
 }

 /**
 * Constructs an empty insertion-ordered {@code LinkedHashMap} instance
 * with the default initial capacity (16) and load factor (0.75).
 */
 public LinkedHashMap() {
 super();
 accessOrder = false;
 }

 /**
 * Constructs an insertion-ordered {@code LinkedHashMap} instance with
 * the same mappings as the specified map. The {@code LinkedHashMap}
 * 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
 * @throws NullPointerException if the specified map is null
 */
 public LinkedHashMap(Map<? extends K, ? extends V> m) {
 super();
 accessOrder = false;
 putMapEntries(m, false);
 }

 /**
 * Constructs an empty {@code LinkedHashMap} 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 - {@code true} for
 * access-order, {@code false} for insertion-order
 * @throws IllegalArgumentException if the initial capacity is negative
 * or the load factor is nonpositive
 */
 public LinkedHashMap(int initialCapacity,
 float loadFactor,
 boolean accessOrder) {
 super(initialCapacity, loadFactor);
 this.accessOrder = accessOrder;
 }


 /**
 * Returns {@code true} 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 {@code true} if this map maps one or more keys to the
 * specified value
 */
 public boolean containsValue(Object value) {
 for (LinkedHashMap.Entry<K,V> e = head; e != null; e = e.after) {
 V v = e.value;
 if (v == value || (value != null && value.equals(v)))
 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.
 */
 public V get(Object key) {
 Node<K,V> e;
 if ((e = getNode(hash(key), key)) == null)
 return null;
 if (accessOrder)
 afterNodeAccess(e);
 return e.value;
 }

 /**
 * {@inheritDoc}
 */
 public V getOrDefault(Object key, V defaultValue) {
 Node<K,V> e;
 if ((e = getNode(hash(key), key)) == null)
 return defaultValue;
 if (accessOrder)
 afterNodeAccess(e);
 return e.value;
 }

 /**
 * {@inheritDoc}
 */
 public void clear() {
 super.clear();
 head = tail = null;
 }

 /**
 * Returns {@code true} if this map should remove its eldest entry.
 * This method is invoked by {@code put} and {@code putAll} 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() &gt; 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
 * {@code false} (indicating that the map should not attempt any
 * further modification). The effects of returning {@code true}
 * after modifying the map from within this method are unspecified.
 *
 * <p>This implementation merely returns {@code false} (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 {@code true}. If the map was empty prior
 * to the {@code put} or {@code putAll} 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 {@code true} if the eldest entry should be removed
 * from the map; {@code false} if it should be retained.
 */
 protected boolean removeEldestEntry(Map.Entry<K,V> eldest) {
 return false;
 }

 /**
 * Returns a {@link Set} view of the keys contained in this map.
 * The set is backed by the map, so changes to the map are
 * reflected in the set, and vice-versa. If the map is modified
 * while an iteration over the set is in progress (except through
 * the iterator's own {@code remove} operation), the results of
 * the iteration are undefined. The set supports element removal,
 * which removes the corresponding mapping from the map, via the
 * {@code Iterator.remove}, {@code Set.remove},
 * {@code removeAll}, {@code retainAll}, and {@code clear}
 * operations. It does not support the {@code add} or {@code addAll}
 * operations.
 * Its {@link Spliterator} typically provides faster sequential
 * performance but much poorer parallel performance than that of
 * {@code HashMap}.
 *
 * @return a set view of the keys contained in this map
 */
 public Set<K> keySet() {
 Set<K> ks = keySet;
 if (ks == null) {
 ks = new LinkedKeySet();
 keySet = ks;
 }
 return ks;
 }

 final class LinkedKeySet extends AbstractSet<K> {
 public final int size() { return size; }
 public final void clear() { LinkedHashMap.this.clear(); }
 public final Iterator<K> iterator() {
 return new LinkedKeyIterator();
 }
 public final boolean contains(Object o) { return containsKey(o); }
 public final boolean remove(Object key) {
 return removeNode(hash(key), key, null, false, true) != null;
 }
 public final Spliterator<K> spliterator() {
 return Spliterators.spliterator(this, Spliterator.SIZED |
 Spliterator.ORDERED |
 Spliterator.DISTINCT);
 }
 public final void forEach(Consumer<? super K> action) {
 if (action == null)
 throw new NullPointerException();
 int mc = modCount;
 for (LinkedHashMap.Entry<K,V> e = head; e != null; e = e.after)
 action.accept(e.key);
 if (modCount != mc)
 throw new ConcurrentModificationException();
 }
 }

 /**
 * Returns a {@link Collection} view of the values contained in this map.
 * The collection is backed by the map, so changes to the map are
 * reflected in the collection, and vice-versa. If the map is
 * modified while an iteration over the collection is in progress
 * (except through the iterator's own {@code remove} operation),
 * the results of the iteration are undefined. The collection
 * supports element removal, which removes the corresponding
 * mapping from the map, via the {@code Iterator.remove},
 * {@code Collection.remove}, {@code removeAll},
 * {@code retainAll} and {@code clear} operations. It does not
 * support the {@code add} or {@code addAll} operations.
 * Its {@link Spliterator} typically provides faster sequential
 * performance but much poorer parallel performance than that of
 * {@code HashMap}.
 *
 * @return a view of the values contained in this map
 */
 public Collection<V> values() {
 Collection<V> vs = values;
 if (vs == null) {
 vs = new LinkedValues();
 values = vs;
 }
 return vs;
 }

 final class LinkedValues extends AbstractCollection<V> {
 public final int size() { return size; }
 public final void clear() { LinkedHashMap.this.clear(); }
 public final Iterator<V> iterator() {
 return new LinkedValueIterator();
 }
 public final boolean contains(Object o) { return containsValue(o); }
 public final Spliterator<V> spliterator() {
 return Spliterators.spliterator(this, Spliterator.SIZED |
 Spliterator.ORDERED);
 }
 public final void forEach(Consumer<? super V> action) {
 if (action == null)
 throw new NullPointerException();
 int mc = modCount;
 for (LinkedHashMap.Entry<K,V> e = head; e != null; e = e.after)
 action.accept(e.value);
 if (modCount != mc)
 throw new ConcurrentModificationException();
 }
 }

 /**
 * Returns a {@link Set} view of the mappings contained in this map.
 * The set is backed by the map, so changes to the map are
 * reflected in the set, and vice-versa. If the map is modified
 * while an iteration over the set is in progress (except through
 * the iterator's own {@code remove} operation, or through the
 * {@code setValue} operation on a map entry returned by the
 * iterator) the results of the iteration are undefined. The set
 * supports element removal, which removes the corresponding
 * mapping from the map, via the {@code Iterator.remove},
 * {@code Set.remove}, {@code removeAll}, {@code retainAll} and
 * {@code clear} operations. It does not support the
 * {@code add} or {@code addAll} operations.
 * Its {@link Spliterator} typically provides faster sequential
 * performance but much poorer parallel performance than that of
 * {@code HashMap}.
 *
 * @return a set view of the mappings contained in this map
 */
 public Set<Map.Entry<K,V>> entrySet() {
 Set<Map.Entry<K,V>> es;
 return (es = entrySet) == null ? (entrySet = new LinkedEntrySet()) : es;
 }

 final class LinkedEntrySet extends AbstractSet<Map.Entry<K,V>> {
 public final int size() { return size; }
 public final void clear() { LinkedHashMap.this.clear(); }
 public final Iterator<Map.Entry<K,V>> iterator() {
 return new LinkedEntryIterator();
 }
 public final boolean contains(Object o) {
 if (!(o instanceof Map.Entry))
 return false;
 Map.Entry<?,?> e = (Map.Entry<?,?>) o;
 Object key = e.getKey();
 Node<K,V> candidate = getNode(hash(key), key);
 return candidate != null && candidate.equals(e);
 }
 public final boolean remove(Object o) {
 if (o instanceof Map.Entry) {
 Map.Entry<?,?> e = (Map.Entry<?,?>) o;
 Object key = e.getKey();
 Object value = e.getValue();
 return removeNode(hash(key), key, value, true, true) != null;
 }
 return false;
 }
 public final Spliterator<Map.Entry<K,V>> spliterator() {
 return Spliterators.spliterator(this, Spliterator.SIZED |
 Spliterator.ORDERED |
 Spliterator.DISTINCT);
 }
 public final void forEach(Consumer<? super Map.Entry<K,V>> action) {
 if (action == null)
 throw new NullPointerException();
 int mc = modCount;
 for (LinkedHashMap.Entry<K,V> e = head; e != null; e = e.after)
 action.accept(e);
 if (modCount != mc)
 throw new ConcurrentModificationException();
 }
 }

 // Map overrides

 public void forEach(BiConsumer<? super K, ? super V> action) {
 if (action == null)
 throw new NullPointerException();
 int mc = modCount;
 for (LinkedHashMap.Entry<K,V> e = head; e != null; e = e.after)
 action.accept(e.key, e.value);
 if (modCount != mc)
 throw new ConcurrentModificationException();
 }

 public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) {
 if (function == null)
 throw new NullPointerException();
 int mc = modCount;
 for (LinkedHashMap.Entry<K,V> e = head; e != null; e = e.after)
 e.value = function.apply(e.key, e.value);
 if (modCount != mc)
 throw new ConcurrentModificationException();
 }

 // Iterators

 abstract class LinkedHashIterator {
 LinkedHashMap.Entry<K,V> next;
 LinkedHashMap.Entry<K,V> current;
 int expectedModCount;

 LinkedHashIterator() {
 next = head;
 expectedModCount = modCount;
 current = null;
 }

 public final boolean hasNext() {
 return next != null;
 }

 final LinkedHashMap.Entry<K,V> nextNode() {
 LinkedHashMap.Entry<K,V> e = next;
 if (modCount != expectedModCount)
 throw new ConcurrentModificationException();
 if (e == null)
 throw new NoSuchElementException();
 current = e;
 next = e.after;
 return e;
 }

 public final void remove() {
 Node<K,V> p = current;
 if (p == null)
 throw new IllegalStateException();
 if (modCount != expectedModCount)
 throw new ConcurrentModificationException();
 current = null;
 removeNode(p.hash, p.key, null, false, false);
 expectedModCount = modCount;
 }
 }

 final class LinkedKeyIterator extends LinkedHashIterator
 implements Iterator<K> {
 public final K next() { return nextNode().getKey(); }
 }

 final class LinkedValueIterator extends LinkedHashIterator
 implements Iterator<V> {
 public final V next() { return nextNode().value; }
 }

 final class LinkedEntryIterator extends LinkedHashIterator
 implements Iterator<Map.Entry<K,V>> {
 public final Map.Entry<K,V> next() { return nextNode(); }
 }


}