HashMap原理(三):容量、加载因子、大小的含义

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package java.util;

import java.io.IOException;
import java.io.InvalidObjectException;
import java.io.Serializable;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.util.function.BiConsumer;
import java.util.function.BiFunction;
import java.util.function.Consumer;
import java.util.function.Function;

/**

• Hash table based implementation of the Map interface. This

• implementation provides all of the optional map operations, and permits

• null values and the null key. (The HashMap

• class is roughly equivalent to Hashtable, except that it is

• unsynchronized and permits nulls.) This class makes no guarantees as to

• the order of the map; in particular, it does not guarantee that the order

• will remain constant over time.

• This implementation provides constant-time performance for the basic

• operations (get and put), assuming the hash function

• disperses the elements properly among the buckets. Iteration over

• collection views requires time proportional to the “capacity” of the

• HashMap instance (the number of buckets) plus its size (the number

• of key-value mappings). Thus, it’s very important not to set the initial

• capacity too high (or the load factor too low) if iteration performance is

• important.

• An instance of HashMap has two parameters that affect its

• performance: initial capacity and load factor. The

• capacity is the number of buckets in the hash table, and the initial

• capacity is simply the capacity at the time the hash table is created. The

• load factor is a measure of how full the hash table is allowed to

• get before its capacity is automatically increased. When the number of

• entries in the hash table exceeds the product of the load factor and the

• current capacity, the hash table is rehashed (that is, internal data

• structures are rebuilt) so that the hash table has approximately twice the

• number of buckets.

• As a general rule, the default load factor (.75) offers a good

• tradeoff between time and space costs. Higher values decrease the

• space overhead but increase the lookup cost (reflected in most of

• the operations of the HashMap class, including

• get and put). The expected number of entries in

• the map and its load factor should be taken into account when

• setting its initial capacity, so as to minimize the number of

• rehash operations. If the initial capacity is greater than the

• maximum number of entries divided by the load factor, no rehash

• operations will ever occur.

• If many mappings are to be stored in a HashMap

• instance, creating it with a sufficiently large capacity will allow

• the mappings to be stored more efficiently than letting it perform

• automatic rehashing as needed to grow the table. Note that using

• many keys with the same {@code hashCode()} is a sure way to slow

• down performance of any hash table. To ameliorate impact, when keys

• are {@link Comparable}, this class may use comparison order among

• keys to help break ties.

• Note that this implementation is not synchronized.

• If multiple threads access a hash map concurrently, and at least one of

• the threads modifies the map structurally, it must be

• synchronized externally. (A structural modification is any operation

• that adds or deletes one or more mappings; merely changing the value

• associated with a key that an instance already contains is not a

• structural modification.) 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:

• Map m = Collections.synchronizedMap(new HashMap(…));

• The iterators returned by all of this class's "collection view methods"

• are fail-fast: if the map is structurally modified at any time after

• the iterator is created, in any way except through the iterator’s own

• 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.

• 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 ConcurrentModificationException on a best-effort basis.

• Therefore, it would be wrong to write a program that depended on this

• exception for its correctness: the fail-fast behavior of iterators

• should be used only to detect bugs.

• This class is a member of the

• Java Collections Framework.

• @param the type of keys maintained by this map

• @param the type of mapped values

• @author Doug Lea

• @author Josh Bloch

• @author Arthur van Hoff

• @author Neal Gafter

• @see Object#hashCode()

• @see Collection

• @see Map

• @see TreeMap

• @see Hashtable

• @since 1.2
  */
  public class HashMap<K,V> extends AbstractMap<K,V>
  implements Map<K,V>, Cloneable, Serializable {

  private static final long serialVersionUID = 362498820763181265L;

  /*

  • Implementation notes.
  • This map usually acts as a binned (bucketed) hash table, but
  • when bins get too large, they are transformed into bins of
  • TreeNodes, each structured similarly to those in
  • java.util.TreeMap. Most methods try to use normal bins, but
  • relay to TreeNode methods when applicable (simply by checking
  • instanceof a node). Bins of TreeNodes may be traversed and
  • used like any others, but additionally support faster lookup
  • when overpopulated. However, since the vast majority of bins in
  • normal use are not overpopulated, checking for existence of
  • tree bins may be delayed in the course of table methods.
  • Tree bins (i.e., bins whose elements are all TreeNodes) are
  • ordered primarily by hashCode, but in the case of ties, if two
  • elements are of the same “class C implements Comparable”,
  • type then their compareTo method is used for ordering. (We
  • conservatively check generic types via reflection to validate
  • this – see method comparableClassFor). The added complexity
  • of tree bins is worthwhile in providing worst-case O(log n)
  • operations when keys either have distinct hashes or are
  • orderable, Thus, performance degrades gracefully under
  • accidental or malicious usages in which hashCode() methods
  • return values that are poorly distributed, as well as those in
  • which many keys share a hashCode, so long as they are also
  • Comparable. (If neither of these apply, we may waste about a
  • factor of two in time and space compared to taking no
  • precautions. But the only known cases stem from poor user
  • programming practices that are already so slow that this makes
  • little difference.)
  • Because TreeNodes are about twice the size of regular nodes, we
  • use them only when bins contain enough nodes to warrant use
  • (see TREEIFY_THRESHOLD). And when they become too small (due to
  • removal or resizing) they are converted back to plain bins. In
  • usages with well-distributed user hashCodes, tree bins are
  • rarely used. Ideally, under random hashCodes, the frequency of
  • nodes in bins follows a Poisson distribution
  • (http://en.wikipedia.org/wiki/Poisson_distribution) with a
  • parameter of about 0.5 on average for the default resizing
  • threshold of 0.75, although with a large variance because of
  • resizing granularity. Ignoring variance, the expected
  • occurrences of list size k are (exp(-0.5) * pow(0.5, k) /
  • factorial(k)). The first values are:
  • 0: 0.60653066
  • 1: 0.30326533
  • 2: 0.07581633
  • 3: 0.01263606
  • 4: 0.00157952
  • 5: 0.00015795
  • 6: 0.00001316
  • 7: 0.00000094
  • 8: 0.00000006
  • more: less than 1 in ten million
  • The root of a tree bin is normally its first node. However,
  • sometimes (currently only upon Iterator.remove), the root might
  • be elsewhere, but can be recovered following parent links
  • (method TreeNode.root()).
  • All applicable internal methods accept a hash code as an
  • argument (as normally supplied from a public method), allowing
  • them to call each other without recomputing user hashCodes.
  • Most internal methods also accept a “tab” argument, that is
  • normally the current table, but may be a new or old one when
  • resizing or converting.
  • When bin lists are treeified, split, or untreeified, we keep
  • them in the same relative access/traversal order (i.e., field
  • Node.next) to better preserve locality, and to slightly
  • simplify handling of splits and traversals that invoke
  • iterator.remove. When using comparators on insertion, to keep a
  • total ordering (or as close as is required here) across
  • rebalancings, we compare classes and identityHashCodes as
  • tie-breakers.
  • The use and transitions among plain vs tree modes is
  • complicated by the existence of subclass LinkedHashMap. See
  • below for hook methods defined to be invoked upon insertion,
  • removal and access that allow LinkedHashMap internals to
  • otherwise remain independent of these mechanics. (This also
  • requires that a map instance be passed to some utility methods
  • that may create new nodes.)
  • The concurrent-programming-like SSA-based coding style helps
  • avoid aliasing errors amid all of the twisty pointer operations.
    */

  /**

  • The default initial capacity - MUST be a power of two.
    */
    static final int DEFAULT_INITIAL_CAPACITY = 1 << 4; // aka 16

  /**

  • The maximum capacity, used if a higher value is implicitly specified
  • by either of the constructors with arguments.
  • MUST be a power of two <= 1<<30.
    */
    static final int MAXIMUM_CAPACITY = 1 << 30;

  /**

  • The load factor used when none specified in constructor.
    */
    static final float DEFAULT_LOAD_FACTOR = 0.75f;

  /**

  • The bin count threshold for using a tree rather than list for a
  • bin. Bins are converted to trees when adding an element to a
  • bin with at least this many nodes. The value must be greater
  • than 2 and should be at least 8 to mesh with assumptions in
  • tree removal about conversion back to plain bins upon
  • shrinkage.
    */
    static final int TREEIFY_THRESHOLD = 8;

  /**

  • The bin count threshold for untreeifying a (split) bin during a
  • resize operation. Should be less than TREEIFY_THRESHOLD, and at
  • most 6 to mesh with shrinkage detection under removal.
    */
    static final int UNTREEIFY_THRESHOLD = 6;

  /**

  • The smallest table capacity for which bins may be treeified.
  • (Otherwise the table is resized if too many nodes in a bin.)
  • Should be at least 4 * TREEIFY_THRESHOLD to avoid conflicts
  • between resizing and treeification thresholds.
    */
    static final int MIN_TREEIFY_CAPACITY = 64;

  /**

  • Basic hash bin node, used for most entries. (See below for

  • TreeNode subclass, and in LinkedHashMap for its Entry subclass.)
    */
    static class Node<K,V> implements Map.Entry<K,V> {
    final int hash;
    final K key;
    V value;
    Node<K,V> next;

    Node(int hash, K key, V value, Node<K,V> next) {
    this.hash = hash;
    this.key = key;
    this.value = value;
    this.next = next;
    }

    public final K getKey() { return key; }
    public final V getValue() { return value; }
    public final String toString() { return key + “=” + value; }

    public final int hashCode() {
    return Objects.hashCode(key) ^ Objects.hashCode(value);
    }

    public final V setValue(V newValue) {
    V oldValue = value;
    value = newValue;
    return oldValue;
    }

    public final boolean equals(Object o) {
    if (o == this)
    return true;
    if (o instanceof Map.Entry) {
    Map.Entry<?,?> e = (Map.Entry<?,?>)o;
    if (Objects.equals(key, e.getKey()) &&
    Objects.equals(value, e.getValue()))
    return true;
    }
    return false;
    }
    }

  /* ---------------- Static utilities -------------- */

  /**

  • Computes key.hashCode() and spreads (XORs) higher bits of hash
  • to lower. Because the table uses power-of-two masking, sets of
  • hashes that vary only in bits above the current mask will
  • always collide. (Among known examples are sets of Float keys
  • holding consecutive whole numbers in small tables.) So we
  • apply a transform that spreads the impact of higher bits
  • downward. There is a tradeoff between speed, utility, and
  • quality of bit-spreading. Because many common sets of hashes
  • are already reasonably distributed (so don’t benefit from
  • spreading), and because we use trees to handle large sets of
  • collisions in bins, we just XOR some shifted bits in the
  • cheapest possible way to reduce systematic lossage, as well as
  • to incorporate impact of the highest bits that would otherwise
  • never be used in index calculations because of table bounds.
    */
    static final int hash(Object key) {
    int h;
    return (key == null) ? 0 : (h = key.hashCode()) ^ (h >>> 16);
    }

  /**

  • Returns x’s Class if it is of the form "class C implements
  • Comparable", else null.
    */
    static Class<?> comparableClassFor(Object x) { if (x instanceof Comparable) { Class<?> c; Type[] ts, as; Type t; ParameterizedType p;
    if ((c = x.getClass()) == String.class) // bypass checks
    return c;
    if ((ts = c.getGenericInterfaces()) != null) {
    for (int i = 0; i < ts.length; ++i) {
    if (((t = ts[i]) instanceof ParameterizedType) &&
    ((p = (ParameterizedType)t).getRawType() ==
    Comparable.class) &&
    (as = p.getActualTypeArguments()) != null &&
    as.length == 1 && as[0] == c) // type arg is c
    return c;
    }
    }
    }
    return null;
    }

  /**

  • Returns k.compareTo(x) if x matches kc (k’s screened comparable
  • class), else 0.
    */
    @SuppressWarnings({“rawtypes”,“unchecked”}) // for cast to Comparable
    static int compareComparables(Class<?> kc, Object k, Object x) {
    return (x == null || x.getClass() != kc ? 0 :
    ((Comparable)k).compareTo(x));
    }

  /**

  • Returns a power of two size for the given target capacity.
    */
    static final int tableSizeFor(int cap) {
    int n = cap - 1;
    n |= n >>> 1;
    n |= n >>> 2;
    n |= n >>> 4;
    n |= n >>> 8;
    n |= n >>> 16;
    return (n < 0) ? 1 : (n >= MAXIMUM_CAPACITY) ? MAXIMUM_CAPACITY : n + 1;
    }

  /* ---------------- Fields -------------- */

  /**

  • The table, initialized on first use, and resized as
  • necessary. When allocated, length is always a power of two.
  • (We also tolerate length zero in some operations to allow
  • bootstrapping mechanics that are currently not needed.)
    */
    transient Node<K,V>[] table;

  /**

  • Holds cached entrySet(). Note that AbstractMap fields are used
  • for keySet() and values().
    */
    transient Set<Map.Entry<K,V>> entrySet;

  /**

  • The number of key-value mappings contained in this map.
    */
    transient int size;

  /**

  • The number of times this HashMap has been structurally modified
  • Structural modifications are those that change the number of mappings in
  • the HashMap or otherwise modify its internal structure (e.g.,
  • rehash). This field is used to make iterators on Collection-views of
  • the HashMap fail-fast. (See ConcurrentModificationException).
    */
    transient int modCount;

  /**

  • The next size value at which to resize (capacity * load factor).
  • @serial
    */
    // (The javadoc description is true upon serialization.
    // Additionally, if the table array has not been allocated, this
    // field holds the initial array capacity, or zero signifying
    // DEFAULT_INITIAL_CAPACITY.)
    int threshold;

  /**

  • The load factor for the hash table.
  • @serial
    */
    final float loadFactor;

  /* ---------------- Public operations -------------- */

  /**

  • Constructs an empty HashMap 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 HashMap(int initialCapacity, float loadFactor) {
  if (initialCapacity < 0)
  throw new IllegalArgumentException("Illegal initial capacity: " +
  initialCapacity);
  if (initialCapacity > MAXIMUM_CAPACITY)
  initialCapacity = MAXIMUM_CAPACITY;
  if (loadFactor <= 0 || Float.isNaN(loadFactor))
  throw new IllegalArgumentException("Illegal load factor: " +
  loadFactor);
  this.loadFactor = loadFactor;
  this.threshold = tableSizeFor(initialCapacity);
  }

  /**

  • Constructs an empty HashMap with the specified initial
  • capacity and the default load factor (0.75).
  • @param initialCapacity the initial capacity.
  • @throws IllegalArgumentException if the initial capacity is negative.
    */
    public HashMap(int initialCapacity) {
    this(initialCapacity, DEFAULT_LOAD_FACTOR);
    }

  /**

  • Constructs an empty HashMap with the default initial capacity
  • (16) and the default load factor (0.75).
    */
    public HashMap() {
    this.loadFactor = DEFAULT_LOAD_FACTOR; // all other fields defaulted
    }

  /**

  • Constructs a new HashMap with the same mappings as the
  • specified Map. The HashMap is created with
  • 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 HashMap(Map<? extends K, ? extends V> m) {
    this.loadFactor = DEFAULT_LOAD_FACTOR;
    putMapEntries(m, false);
    }

  /**

  • Implements Map.putAll and Map constructor
  • @param m the map
  • @param evict false when initially constructing this map, else
  • true (relayed to method afterNodeInsertion).
    */
    final void putMapEntries(Map<? extends K, ? extends V> m, boolean evict) {
    int s = m.size();
    if (s > 0) {
    if (table == null) { // pre-size
    float ft = ((float)s / loadFactor) + 1.0F;
    int t = ((ft < (float)MAXIMUM_CAPACITY) ?
    (int)ft : MAXIMUM_CAPACITY);
    if (t > threshold)
    threshold = tableSizeFor(t);
    }
    else if (s > threshold)
    resize();
    for (Map.Entry<? extends K, ? extends V> e : m.entrySet()) {
    K key = e.getKey();
    V value = e.getValue();
    putVal(hash(key), key, value, false, evict);
    }
    }
    }

  /**

  • Returns the number of key-value mappings in this map.
  • @return the number of key-value mappings in this map
    */
    public int size() {
    return size;
    }

  /**

  • Returns true if this map contains no key-value mappings.
  • @return true if this map contains no key-value mappings
    */
    public boolean isEmpty() {
    return size == 0;
    }

  /**

  • Returns the value to which the specified key is mapped,
  • or {@code null} if this map contains no mapping for the key.

  • More formally, if this map contains a mapping from a key

  • {@code k} to a value {@code v} such that {@code (keynull ? knull :
  • key.equals(k))}, then this method returns {@code v}; otherwise
  • it returns {@code null}. (There can be at most one such mapping.)

  • A return value of {@code null} does not necessarily

  • 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.
  • @see #put(Object, Object)
    */
    public V get(Object key) {
    Node<K,V> e;
    return (e = getNode(hash(key), key)) == null ? null : e.value;
    }

  /**

  • Implements Map.get and related methods
  • @param hash hash for key
  • @param key the key
  • @return the node, or null if none
    */
    final Node<K,V> getNode(int hash, Object key) {
    Node<K,V>[] tab; Node<K,V> first, e; int n; K k;
    if ((tab = table) != null && (n = tab.length) > 0 &&
    (first = tab[(n - 1) & hash]) != null) {
    if (first.hash == hash && // always check first node
    ((k = first.key) == key || (key != null && key.equals(k))))
    return first;
    if ((e = first.next) != null) {
    if (first instanceof TreeNode)
    return ((TreeNode<K,V>)first).getTreeNode(hash, key);
    do {
    if (e.hash == hash &&
    ((k = e.key) == key || (key != null && key.equals(k))))
    return e;
    } while ((e = e.next) != null);
    }
    }
    return null;
    }

  /**

  • Returns true if this map contains a mapping for the
  • specified key.
  • @param key The key whose presence in this map is to be tested
  • @return true if this map contains a mapping for the specified
  • key.
    */
    public boolean containsKey(Object key) {
    return getNode(hash(key), key) != null;
    }

  /**

  • Associates the specified value with the specified key in this map.
  • If the map previously contained a mapping for the key, the old
  • value is replaced.
  • @param key key with which the specified value is to be associated
  • @param value value to be associated with the specified key
  • @return the previous value associated with key, or

  •     <tt>null</tt> if there was no mapping for <tt>key</tt>.
    

  •     (A <tt>null</tt> return can also indicate that the map
    

  •     previously associated <tt>null</tt> with <tt>key</tt>.)
    

  */
  public V put(K key, V value) {
  return putVal(hash(key), key, value, false, true);
  }

  /**

  • Implements Map.put and related methods
  • @param hash hash for key
  • @param key the key
  • @param value the value to put
  • @param onlyIfAbsent if true, don’t change existing value
  • @param evict if false, the table is in creation mode.
  • @return previous value, or null if none
    */
    final V putVal(int hash, K key, V value, boolean onlyIfAbsent,
    boolean evict) {
    Node<K,V>[] tab; Node<K,V> p; int n, i;
    if ((tab = table) == null || (n = tab.length) == 0)
    n = (tab = resize()).length;
    if ((p = tab[i = (n - 1) & hash]) == null)
    tab[i] = newNode(hash, key, value, null);
    else {
    Node<K,V> e; K k;
    if (p.hash == hash &&
    ((k = p.key) == key || (key != null && key.equals(k))))
    e = p;
    else if (p instanceof TreeNode)
    e = ((TreeNode<K,V>)p).putTreeVal(this, tab, hash, key, value);
    else {
    for (int binCount = 0; ; ++binCount) {
    if ((e = p.next) == null) {
    p.next = newNode(hash, key, value, null);
    if (binCount >= TREEIFY_THRESHOLD - 1) // -1 for 1st
    treeifyBin(tab, hash);
    break;
    }
    if (e.hash == hash &&
    ((k = e.key) == key || (key != null && key.equals(k))))
    break;
    p = e;
    }
    }
    if (e != null) { // existing mapping for key
    V oldValue = e.value;
    if (!onlyIfAbsent || oldValue == null)
    e.value = value;
    afterNodeAccess(e);
    return oldValue;
    }
    }
    ++modCount;
    if (++size > threshold)
    resize();
    afterNodeInsertion(evict);
    return null;
    }

  /**

  • Initializes or doubles table size. If null, allocates in
  • accord with initial capacity target held in field threshold.
  • Otherwise, because we are using power-of-two expansion, the
  • elements from each bin must either stay at same index, or move
  • with a power of two offset in the new table.
  • @return the table
    */
    final Node<K,V>[] resize() {
    Node<K,V>[] oldTab = table;
    int oldCap = (oldTab == null) ? 0 : oldTab.length;
    int oldThr = threshold;
    int newCap, newThr = 0;
    if (oldCap > 0) {
    if (oldCap >= MAXIMUM_CAPACITY) {
    threshold = Integer.MAX_VALUE;
    return oldTab;
    }
    else if ((newCap = oldCap << 1) < MAXIMUM_CAPACITY &&
    oldCap >= DEFAULT_INITIAL_CAPACITY)
    newThr = oldThr << 1; // double threshold
    }
    else if (oldThr > 0) // initial capacity was placed in threshold
    newCap = oldThr;
    else { // zero initial threshold signifies using defaults
    newCap = DEFAULT_INITIAL_CAPACITY;
    newThr = (int)(DEFAULT_LOAD_FACTOR * DEFAULT_INITIAL_CAPACITY);
    }
    if (newThr == 0) {
    float ft = (float)newCap * loadFactor;
    newThr = (newCap < MAXIMUM_CAPACITY && ft < (float)MAXIMUM_CAPACITY ?
    (int)ft : Integer.MAX_VALUE);
    }
    threshold = newThr;
    @SuppressWarnings({“rawtypes”,“unchecked”})
    Node<K,V>[] newTab = (Node<K,V>[])new Node[newCap];
    table = newTab;
    if (oldTab != null) {
    for (int j = 0; j < oldCap; ++j) {
    Node<K,V> e;
    if ((e = oldTab[j]) != null) {
    oldTab[j] = null;
    if (e.next == null)
    newTab[e.hash & (newCap - 1)] = e;
    else if (e instanceof TreeNode)
    ((TreeNode<K,V>)e).split(this, newTab, j, oldCap);
    else { // preserve order
    Node<K,V> loHead = null, loTail = null;
    Node<K,V> hiHead = null, hiTail = null;
    Node<K,V> next;
    do {
    next = e.next;
    if ((e.hash & oldCap) == 0) {
    if (loTail == null)
    loHead = e;
    else
    loTail.next = e;
    loTail = e;
    }
    else {
    if (hiTail == null)
    hiHead = e;
    else
    hiTail.next = e;
    hiTail = e;
    }
    } while ((e = next) != null);
    if (loTail != null) {
    loTail.next = null;
    newTab[j] = loHead;
    }
    if (hiTail != null) {
    hiTail.next = null;
    newTab[j + oldCap] = hiHead;
    }
    }
    }
    }
    }
    return newTab;
    }

  /**

  • Replaces all linked nodes in bin at index for given hash unless
  • table is too small, in which case resizes instead.
    */
    final void treeifyBin(Node<K,V>[] tab, int hash) {
    int n, index; Node<K,V> e;
    if (tab == null || (n = tab.length) < MIN_TREEIFY_CAPACITY)
    resize();
    else if ((e = tab[index = (n - 1) & hash]) != null) {
    TreeNode<K,V> hd = null, tl = null;
    do {
    TreeNode<K,V> p = replacementTreeNode(e, null);
    if (tl == null)
    hd = p;
    else {
    p.prev = tl;
    tl.next = p;
    }
    tl = p;
    } while ((e = e.next) != null);
    if ((tab[index] = hd) != null)
    hd.treeify(tab);
    }
    }

  /**

  • Copies all of the mappings from the specified map to this map.
  • These mappings will replace any mappings that this map had for
  • any of the keys currently in the specified map.
  • @param m mappings to be stored in this map
  • @throws NullPointerException if the specified map is null
    */
    public void putAll(Map<? extends K, ? extends V> m) {
    putMapEntries(m, true);
    }

  /**

  • Removes the mapping for the specified key from this map if present.
  • @param key key whose mapping is to be removed from the map
  • @return the previous value associated with key, or

  •     <tt>null</tt> if there was no mapping for <tt>key</tt>.
    

  •     (A <tt>null</tt> return can also indicate that the map
    

  •     previously associated <tt>null</tt> with <tt>key</tt>.)
    

  */
  public V remove(Object key) {
  Node<K,V> e;
  return (e = removeNode(hash(key), key, null, false, true)) == null ?
  null : e.value;
  }

  /**

  • Implements Map.remove and related methods
  • @param hash hash for key
  • @param key the key
  • @param value the value to match if matchValue, else ignored
  • @param matchValue if true only remove if value is equal
  • @param movable if false do not move other nodes while removing
  • @return the node, or null if none
    */
    final Node<K,V> removeNode(int hash, Object key, Object value,
    boolean matchValue, boolean movable) {
    Node<K,V>[] tab; Node<K,V> p; int n, index;
    if ((tab = table) != null && (n = tab.length) > 0 &&
    (p = tab[index = (n - 1) & hash]) != null) {
    Node<K,V> node = null, e; K k; V v;
    if (p.hash == hash &&
    ((k = p.key) == key || (key != null && key.equals(k))))
    node = p;
    else if ((e = p.next) != null) {
    if (p instanceof TreeNode)
    node = ((TreeNode<K,V>)p).getTreeNode(hash, key);
    else {
    do {
    if (e.hash == hash &&
    ((k = e.key) == key ||
    (key != null && key.equals(k)))) {
    node = e;
    break;
    }
    p = e;
    } while ((e = e.next) != null);
    }
    }
    if (node != null && (!matchValue || (v = node.value) == value ||
    (value != null && value.equals(v)))) {
    if (node instanceof TreeNode)
    ((TreeNode<K,V>)node).removeTreeNode(this, tab, movable);
    else if (node == p)
    tab[index] = node.next;
    else
    p.next = node.next;
    ++modCount;
    –size;
    afterNodeRemoval(node);
    return node;
    }
    }
    return null;
    }

  /**

  • Removes all of the mappings from this map.
  • The map will be empty after this call returns.
    */
    public void clear() {
    Node<K,V>[] tab;
    modCount++;
    if ((tab = table) != null && size > 0) {
    size = 0;
    for (int i = 0; i < tab.length; ++i)
    tab[i] = null;
    }
    }

  /**

  • Returns 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 true if this map maps one or more keys to the

  •     specified value
    

  */
  public boolean containsValue(Object value) {
  Node<K,V>[] tab; V v;
  if ((tab = table) != null && size > 0) {
  for (int i = 0; i < tab.length; ++i) {
  for (Node<K,V> e = tab[i]; e != null; e = e.next) {
  if ((v = e.value) == value ||
  (value != null && value.equals(v)))
  return true;
  }
  }
  }
  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 remove operation), the results of
  • the iteration are undefined. The set supports element removal,
  • which removes the corresponding mapping from the map, via the
  • Iterator.remove, Set.remove,
  • removeAll, retainAll, and clear
  • operations. It does not support the add or addAll
  • operations.
  • @return a set view of the keys contained in this map
    */
    public Set keySet() {
    Set ks = keySet;
    if (ks == null) {
    ks = new KeySet();
    keySet = ks;
    }
    return ks;
    }

  final class KeySet extends AbstractSet {
  public final int size() { return size; }
  public final void clear() { HashMap.this.clear(); }
  public final Iterator iterator() { return new KeyIterator(); }
  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 spliterator() {
  return new KeySpliterator<>(HashMap.this, 0, -1, 0, 0);
  }
  public final void forEach(Consumer<? super K> action) {
  Node<K,V>[] tab;
  if (action == null)
  throw new NullPointerException();
  if (size > 0 && (tab = table) != null) {
  int mc = modCount;
  // Android-changed: Detect changes to modCount early.
  for (int i = 0; (i < tab.length && modCount == mc); ++i) {
  for (Node<K,V> e = tab[i]; e != null; e = e.next)
  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 remove operation),
  • the results of the iteration are undefined. The collection
  • supports element removal, which removes the corresponding
  • mapping from the map, via the Iterator.remove,
  • Collection.remove, removeAll,
  • retainAll and clear operations. It does not
  • support the add or addAll operations.
  • @return a view of the values contained in this map
    */
    public Collection values() {
    Collection vs = values;
    if (vs == null) {
    vs = new Values();
    values = vs;
    }
    return vs;
    }

  final class Values extends AbstractCollection {
  public final int size() { return size; }
  public final void clear() { HashMap.this.clear(); }
  public final Iterator iterator() { return new ValueIterator(); }
  public final boolean contains(Object o) { return containsValue(o); }
  public final Spliterator spliterator() {
  return new ValueSpliterator<>(HashMap.this, 0, -1, 0, 0);
  }
  public final void forEach(Consumer<? super V> action) {
  Node<K,V>[] tab;
  if (action == null)
  throw new NullPointerException();
  if (size > 0 && (tab = table) != null) {
  int mc = modCount;
  // Android-changed: Detect changes to modCount early.
  for (int i = 0; (i < tab.length && modCount == mc); ++i) {
  for (Node<K,V> e = tab[i]; e != null; e = e.next)
  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 remove operation, or through the
  • 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 Iterator.remove,
  • Set.remove, removeAll, retainAll and
  • clear operations. It does not support the
  • add or addAll operations.
  • @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 EntrySet()) : es;
    }

  final class EntrySet extends AbstractSet<Map.Entry<K,V>> {
  public final int size() { return size; }
  public final void clear() { HashMap.this.clear(); }
  public final Iterator<Map.Entry<K,V>> iterator() {
  return new EntryIterator();
  }
  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 new EntrySpliterator<>(HashMap.this, 0, -1, 0, 0);
  }
  public final void forEach(Consumer<? super Map.Entry<K,V>> action) {
  Node<K,V>[] tab;
  if (action == null)
  throw new NullPointerException();
  if (size > 0 && (tab = table) != null) {
  int mc = modCount;
  // Android-changed: Detect changes to modCount early.
  for (int i = 0; (i < tab.length && modCount == mc); ++i) {
  for (Node<K,V> e = tab[i]; e != null; e = e.next)
  action.accept(e);
  }
  if (modCount != mc)
  throw new ConcurrentModificationException();
  }
  }
  }

  // Overrides of JDK8 Map extension methods

  @Override
  public V getOrDefault(Object key, V defaultValue) {
  Node<K,V> e;
  return (e = getNode(hash(key), key)) == null ? defaultValue : e.value;
  }

  @Override
  public V putIfAbsent(K key, V value) {
  return putVal(hash(key), key, value, true, true);
  }

  @Override
  public boolean remove(Object key, Object value) {
  return removeNode(hash(key), key, value, true, true) != null;
  }

  @Override
  public boolean replace(K key, V oldValue, V newValue) {
  Node<K,V> e; V v;
  if ((e = getNode(hash(key), key)) != null &&
  ((v = e.value) == oldValue || (v != null && v.equals(oldValue)))) {
  e.value = newValue;
  afterNodeAccess(e);
  return true;
  }
  return false;
  }

  @Override
  public V replace(K key, V value) {
  Node<K,V> e;
  if ((e = getNode(hash(key), key)) != null) {
  V oldValue = e.value;
  e.value = value;
  afterNodeAccess(e);
  return oldValue;
  }
  return null;
  }

  @Override
  public V computeIfAbsent(K key,
  Function<? super K, ? extends V> mappingFunction) {
  if (mappingFunction == null)
  throw new NullPointerException();
  int hash = hash(key);
  Node<K,V>[] tab; Node<K,V> first; int n, i;
  int binCount = 0;
  TreeNode<K,V> t = null;
  Node<K,V> old = null;
  if (size > threshold || (tab = table) == null ||
  (n = tab.length) == 0)
  n = (tab = resize()).length;
  if ((first = tab[i = (n - 1) & hash]) != null) {
  if (first instanceof TreeNode)
  old = (t = (TreeNode<K,V>)first).getTreeNode(hash, key);
  else {
  Node<K,V> e = first; K k;
  do {
  if (e.hash == hash &&
  ((k = e.key) == key || (key != null && key.equals(k)))) {
  old = e;
  break;
  }
  ++binCount;
  } while ((e = e.next) != null);
  }
  V oldValue;
  if (old != null && (oldValue = old.value) != null) {
  afterNodeAccess(old);
  return oldValue;
  }
  }
  V v = mappingFunction.apply(key);
  if (v == null) {
  return null;
  } else if (old != null) {
  old.value = v;
  afterNodeAccess(old);
  return v;
  }
  else if (t != null)
  t.putTreeVal(this, tab, hash, key, v);
  else {
  tab[i] = newNode(hash, key, v, first);
  if (binCount >= TREEIFY_THRESHOLD - 1)
  treeifyBin(tab, hash);
  }
  ++modCount;
  ++size;
  afterNodeInsertion(true);
  return v;
  }

  public V computeIfPresent(K key,
  BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
  if (remappingFunction == null)
  throw new NullPointerException();
  Node<K,V> e; V oldValue;
  int hash = hash(key);
  if ((e = getNode(hash, key)) != null &&
  (oldValue = e.value) != null) {
  V v = remappingFunction.apply(key, oldValue);
  if (v != null) {
  e.value = v;
  afterNodeAccess(e);
  return v;
  }
  else
  removeNode(hash, key, null, false, true);
  }
  return null;
  }

  @Override
  public V compute(K key,
  BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
  if (remappingFunction == null)
  throw new NullPointerException();
  int hash = hash(key);
  Node<K,V>[] tab; Node<K,V> first; int n, i;
  int binCount = 0;
  TreeNode<K,V> t = null;
  Node<K,V> old = null;
  if (size > threshold || (tab = table) == null ||
  (n = tab.length) == 0)
  n = (tab = resize()).length;
  if ((first = tab[i = (n - 1) & hash]) != null) {
  if (first instanceof TreeNode)
  old = (t = (TreeNode<K,V>)first).getTreeNode(hash, key);
  else {
  Node<K,V> e = first; K k;
  do {
  if (e.hash == hash &&
  ((k = e.key) == key || (key != null && key.equals(k)))) {
  old = e;
  break;
  }
  ++binCount;
  } while ((e = e.next) != null);
  }
  }
  V oldValue = (old == null) ? null : old.value;
  V v = remappingFunction.apply(key, oldValue);
  if (old != null) {
  if (v != null) {
  old.value = v;
  afterNodeAccess(old);
  }
  else
  removeNode(hash, key, null, false, true);
  }
  else if (v != null) {
  if (t != null)
  t.putTreeVal(this, tab, hash, key, v);
  else {
  tab[i] = newNode(hash, key, v, first);
  if (binCount >= TREEIFY_THRESHOLD - 1)
  treeifyBin(tab, hash);
  }
  ++modCount;
  ++size;
  afterNodeInsertion(true);
  }
  return v;
  }

  @Override
  public V merge(K key, V value,
  BiFunction<? super V, ? super V, ? extends V> remappingFunction) {
  if (value == null)
  throw new NullPointerException();
  if (remappingFunction == null)
  throw new NullPointerException();
  int hash = hash(key);
  Node<K,V>[] tab; Node<K,V> first; int n, i;
  int binCount = 0;
  TreeNode<K,V> t = null;
  Node<K,V> old = null;
  if (size > threshold || (tab = table) == null ||
  (n = tab.length) == 0)
  n = (tab = resize()).length;
  if ((first = tab[i = (n - 1) & hash]) != null) {
  if (first instanceof TreeNode)
  old = (t = (TreeNode<K,V>)first).getTreeNode(hash, key);
  else {
  Node<K,V> e = first; K k;
  do {
  if (e.hash == hash &&
  ((k = e.key) == key || (key != null && key.equals(k)))) {
  old = e;
  break;
  }
  ++binCount;
  } while ((e = e.next) != null);
  }
  }
  if (old != null) {
  V v;
  if (old.value != null)
  v = remappingFunction.apply(old.value, value);
  else
  v = value;
  if (v != null) {
  old.value = v;
  afterNodeAccess(old);
  }
  else
  removeNode(hash, key, null, false, true);
  return v;
  }
  if (value != null) {
  if (t != null)
  t.putTreeVal(this, tab, hash, key, value);
  else {
  tab[i] = newNode(hash, key, value, first);
  if (binCount >= TREEIFY_THRESHOLD - 1)
  treeifyBin(tab, hash);
  }
  ++modCount;
  ++size;
  afterNodeInsertion(true);
  }
  return value;
  }

  @Override
  public void forEach(BiConsumer<? super K, ? super V> action) {
  Node<K,V>[] tab;
  if (action == null)
  throw new NullPointerException();
  if (size > 0 && (tab = table) != null) {
  int mc = modCount;
  // Android-changed: Detect changes to modCount early.
  for (int i = 0; (i < tab.length && mc == modCount); ++i) {
  for (Node<K,V> e = tab[i]; e != null; e = e.next)
  action.accept(e.key, e.value);
  }
  if (modCount != mc)
  throw new ConcurrentModificationException();
  }
  }

  @Override
  public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) {
  Node<K,V>[] tab;
  if (function == null)
  throw new NullPointerException();
  if (size > 0 && (tab = table) != null) {
  int mc = modCount;
  for (int i = 0; i < tab.length; ++i) {
  for (Node<K,V> e = tab[i]; e != null; e = e.next) {
  e.value = function.apply(e.key, e.value);
  }
  }
  if (modCount != mc)
  throw new ConcurrentModificationException();
  }
  }

  /* ------------------------------------------------------------ */
  // Cloning and serialization

  /**

  • Returns a shallow copy of this HashMap instance: the keys and
  • values themselves are not cloned.
  • @return a shallow copy of this map
    */
    @SuppressWarnings(“unchecked”)
    @Override
    public Object clone() {
    HashMap<K,V> result;
    try {
    result = (HashMap<K,V>)super.clone();
    } catch (CloneNotSupportedException e) {
    // this shouldn’t happen, since we are Cloneable
    throw new InternalError(e);
    }
    result.reinitialize();
    result.putMapEntries(this, false);
    return result;
    }

  // These methods are also used when serializing HashSets
  final float loadFactor() { return loadFactor; }
  final int capacity() {
  return (table != null) ? table.length :
  (threshold > 0) ? threshold :
  DEFAULT_INITIAL_CAPACITY;
  }

  /**

  • Save the state of the HashMap instance to a stream (i.e.,
  • serialize it).
  • @serialData The capacity of the HashMap (the length of the

  •         bucket array) is emitted (int), followed by the
    

  •         <i>size</i> (an int, the number of key-value
    

  •         mappings), followed by the key (Object) and value (Object)
    

  •         for each key-value mapping.  The key-value mappings are
    

  •         emitted in no particular order.
    

  */
  private void writeObject(java.io.ObjectOutputStream s)
  throws IOException {
  int buckets = capacity();
  // Write out the threshold, loadfactor, and any hidden stuff
  s.defaultWriteObject();
  s.writeInt(buckets);
  s.writeInt(size);
  internalWriteEntries(s);
  }

  /**

  • Reconstitute the {@code HashMap} instance from a stream (i.e.,

  • deserialize it).
    */
    private void readObject(java.io.ObjectInputStream s)
    throws IOException, ClassNotFoundException {
    // Read in the threshold (ignored), loadfactor, and any hidden stuff
    s.defaultReadObject();
    reinitialize();
    if (loadFactor <= 0 || Float.isNaN(loadFactor))
    throw new InvalidObjectException("Illegal load factor: " +
    loadFactor);
    s.readInt(); // Read and ignore number of buckets
    int mappings = s.readInt(); // Read number of mappings (size)
    if (mappings < 0)
    throw new InvalidObjectException("Illegal mappings count: " +
    mappings);
    else if (mappings > 0) { // (if zero, use defaults)
    // Size the table using given load factor only if within
    // range of 0.25…4.0
    float lf = Math.min(Math.max(0.25f, loadFactor), 4.0f);
    float fc = (float)mappings / lf + 1.0f;
    int cap = ((fc < DEFAULT_INITIAL_CAPACITY) ?
    DEFAULT_INITIAL_CAPACITY :
    (fc >= MAXIMUM_CAPACITY) ?
    MAXIMUM_CAPACITY :
    tableSizeFor((int)fc));
    float ft = (float)cap * lf;
    threshold = ((cap < MAXIMUM_CAPACITY && ft < MAXIMUM_CAPACITY) ?
    (int)ft : Integer.MAX_VALUE);
    @SuppressWarnings({“rawtypes”,“unchecked”})
    Node<K,V>[] tab = (Node<K,V>[])new Node[cap];
    table = tab;

     // Read the keys and values, and put the mappings in the HashMap
     for (int i = 0; i < mappings; i++) {
         @SuppressWarnings("unchecked")
             K key = (K) s.readObject();
         @SuppressWarnings("unchecked")
             V value = (V) s.readObject();
         putVal(hash(key), key, value, false, false);
     }
    

    }
    }

  /* ------------------------------------------------------------ */
  // iterators

  abstract class HashIterator {
  Node<K,V> next; // next entry to return
  Node<K,V> current; // current entry
  int expectedModCount; // for fast-fail
  int index; // current slot

   HashIterator() {
       expectedModCount = modCount;
       Node<K,V>[] t = table;
       current = next = null;
       index = 0;
       if (t != null && size > 0) { // advance to first entry
           do {} while (index < t.length && (next = t[index++]) == null);
       }
   }
  
   public final boolean hasNext() {
       return next != null;
   }
  
   final Node<K,V> nextNode() {
       Node<K,V>[] t;
       Node<K,V> e = next;
       if (modCount != expectedModCount)
           throw new ConcurrentModificationException();
       if (e == null)
           throw new NoSuchElementException();
       if ((next = (current = e).next) == null && (t = table) != null) {
           do {} while (index < t.length && (next = t[index++]) == null);
       }
       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;
       K key = p.key;
       removeNode(hash(key), key, null, false, false);
       expectedModCount = modCount;
   }
  

  }文章来源地址https://www.toymoban.com/news/detail-466478.html

  final class KeyIterator extends HashIterator
  implements Iterator {
  public final K next() { return nextNode().key; }
  }

  final class ValueIterator extends HashIterator
  implements Iterator {
  public final V next() { return nextNode().value; }
  }

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

  /* ------------------------------------------------------------ */
  // spliterators

  static class HashMapSpliterator<K,V> {
  final HashMap<K,V> map;
  Node<K,V> current; // current node
  int index; // current index, modified on advance/split
  int fence; // one past last index
  int est; // size estimate
  int expectedModCount; // for comodification checks

   HashMapSpliterator(HashMap<K,V> m, int origin,
                      int fence, int est,
                      int expectedModCount) {
       this.map = m;
       this.index = origin;
       this.fence = fence;
       this.est = est;
       this.expectedModCount = expectedModCount;
   }
  
   final int getFence() { // initialize fence and size on first use
       int hi;
       if ((hi = fence) < 0) {
           HashMap<K,V> m = map;
           est = m.size;
           expectedModCount = m.modCount;
           Node<K,V>[] tab = m.table;
           hi = fence = (tab == null) ? 0 : tab.length;
       }
       return hi;
   }
  
   public final long estimateSize() {
       getFence(); // force init
       return (long) est;
   }
  

  }

  static final class KeySpliterator<K,V>
  extends HashMapSpliterator<K,V>
  implements Spliterator {
  KeySpliterator(HashMap<K,V> m, int origin, int fence, int est,
  int expectedModCount) {
  super(m, origin, fence, est, expectedModCount);
  }

   public KeySpliterator<K,V> trySplit() {
       int hi = getFence(), lo = index, mid = (lo + hi) >>> 1;
       return (lo >= mid || current != null) ? null :
           new KeySpliterator<>(map, lo, index = mid, est >>>= 1,
                                   expectedModCount);
   }
  
   public void forEachRemaining(Consumer<? super K> action) {
       int i, hi, mc;
       if (action == null)
           throw new NullPointerException();
       HashMap<K,V> m = map;
       Node<K,V>[] tab = m.table;
       if ((hi = fence) < 0) {
           mc = expectedModCount = m.modCount;
           hi = fence = (tab == null) ? 0 : tab.length;
       }
       else
           mc = expectedModCount;
       if (tab != null && tab.length >= hi &&
           (i = index) >= 0 && (i < (index = hi) || current != null)) {
           Node<K,V> p = current;
           current = null;
           do {
               if (p == null)
                   p = tab[i++];
               else {
                   action.accept(p.key);
                   p = p.next;
               }
           } while (p != null || i < hi);
           if (m.modCount != mc)
               throw new ConcurrentModificationException();
       }
   }
  
   public boolean tryAdvance(Consumer<? super K> action) {
       int hi;
       if (action == null)
           throw new NullPointerException();
       Node<K,V>[] tab = map.table;
       if (tab != null && tab.length >= (hi = getFence()) && index >= 0) {
           while (current != null || index < hi) {
               if (current == null)
                   current = tab[index++];
               else {
                   K k = current.key;
                   current = current.next;
                   action.accept(k);
                   if (map.modCount != expectedModCount)
                       throw new ConcurrentModificationException();
                   return true;
               }
           }
       }
       return false;
   }
  
   public int characteristics() {
       return (fence < 0 || est == map.size ? Spliterator.SIZED : 0) |
           Spliterator.DISTINCT;
   }
  

  }

  static final class ValueSpliterator<K,V>
  extends HashMapSpliterator<K,V>
  implements Spliterator {
  ValueSpliterator(HashMap<K,V> m, int origin, int fence, int est,
  int expectedModCount) {
  super(m, origin, fence, est, expectedModCount);
  }

   public ValueSpliterator<K,V> trySplit() {
       int hi = getFence(), lo = index, mid = (lo + hi) >>> 1;
       return (lo >= mid || current != null) ? null :
           new ValueSpliterator<>(map, lo, index = mid, est >>>= 1,
                                     expectedModCount);
   }
  
   public void forEachRemaining(Consumer<? super V> action) {
       int i, hi, mc;
       if (action == null)
           throw new NullPointerException();
       HashMap<K,V> m = map;
       Node<K,V>[] tab = m.table;
       if ((hi = fence) < 0) {
           mc = expectedModCount = m.modCount;
           hi = fence = (tab == null) ? 0 : tab.length;
       }
       else
           mc = expectedModCount;
       if (tab != null && tab.length >= hi &&
           (i = index) >= 0 && (i < (index = hi) || current != null)) {
           Node<K,V> p = current;
           current = null;
           do {
               if (p == null)
                   p = tab[i++];
               else {
                   action.accept(p.value);
                   p = p.next;
               }
           } while (p != null || i < hi);
           if (m.modCount != mc)
               throw new ConcurrentModificationException();
       }
   }
  
   public boolean tryAdvance(Consumer<? super V> action) {
       int hi;
       if (action == null)
           throw new NullPointerException();
       Node<K,V>[] tab = map.table;
       if (tab != null && tab.length >= (hi = getFence()) && index >= 0) {
           while (current != null || index < hi) {
               if (current == null)
                   current = tab[index++];
               else {
                   V v = current.value;
                   current = current.next;
                   action.accept(v);
                   if (map.modCount != expectedModCount)
                       throw new ConcurrentModificationException();
                   return true;
               }
           }
       }
       return false;
   }
  
   public int characteristics() {
       return (fence < 0 || est == map.size ? Spliterator.SIZED : 0);
   }
  

  }

  static final class EntrySpliterator<K,V>
  extends HashMapSpliterator<K,V>
  implements Spliterator<Map.Entry<K,V>> {
  EntrySpliterator(HashMap<K,V> m, int origin, int fence, int est,
  int expectedModCount) {
  super(m, origin, fence, est, expectedModCount);
  }

   public EntrySpliterator<K,V> trySplit() {
       int hi = getFence(), lo = index, mid = (lo + hi) >>> 1;
       return (lo >= mid || current != null) ? null :
           new EntrySpliterator<>(map, lo, index = mid, est >>>= 1,
                                     expectedModCount);
   }
  
   public void forEachRemaining(Consumer<? super Map.Entry<K,V>> action) {
       int i, hi, mc;
       if (action == null)
           throw new NullPointerException();
       HashMap<K,V> m = map;
       Node<K,V>[] tab = m.table;
       if ((hi = fence) < 0) {
           mc = expectedModCount = m.modCount;
           hi = fence = (tab == null) ? 0 : tab.length;
       }
       else
           mc = expectedModCount;
       if (tab != null && tab.length >= hi &&
           (i = index) >= 0 && (i < (index = hi) || current != null)) {
           Node<K,V> p = current;
           current = null;
           do {
               if (p == null)
                   p = tab[i++];
               else {
                   action.accept(p);
                   p = p.next;
               }
           } while (p != null || i < hi);
           if (m.modCount != mc)
               throw new ConcurrentModificationException();
       }
   }
  
   public boolean tryAdvance(Consumer<? super Map.Entry<K,V>> action) {
       int hi;
       if (action == null)
           throw new NullPointerException();
       Node<K,V>[] tab = map.table;
       if (tab != null && tab.length >= (hi = getFence()) && index >= 0) {
           while (current != null || index < hi) {
               if (current == null)
                   current = tab[index++];
               else {
                   Node<K,V> e = current;
                   current = current.next;
                   action.accept(e);
                   if (map.modCount != expectedModCount)
                       throw new ConcurrentModificationException();
                   return true;
               }
           }
       }
       return false;
   }
  
   public int characteristics() {
       return (fence < 0 || est == map.size ? Spliterator.SIZED : 0) |
           Spliterator.DISTINCT;
   }
  

  }

  /* ------------------------------------------------------------ */
  // LinkedHashMap support

  /*

  • The following package-protected methods are designed to be
  • overridden by LinkedHashMap, but not by any other subclass.
  • Nearly all other internal methods are also package-protected
  • but are declared final, so can be used by LinkedHashMap, view
  • classes, and HashSet.
    */

  // Create a regular (non-tree) node
  Node<K,V> newNode(int hash, K key, V value, Node<K,V> next) {
  return new Node<>(hash, key, value, next);
  }

  // For conversion from TreeNodes to plain nodes
  Node<K,V> replacementNode(Node<K,V> p, Node<K,V> next) {
  return new Node<>(p.hash, p.key, p.value, next);
  }

  // Create a tree bin node
  TreeNode<K,V> newTreeNode(int hash, K key, V value, Node<K,V> next) {
  return new TreeNode<>(hash, key, value, next);
  }

  // For treeifyBin
  TreeNode<K,V> replacementTreeNode(Node<K,V> p, Node<K,V> next) {
  return new TreeNode<>(p.hash, p.key, p.value, next);
  }

  /**

  • Reset to initial default state. Called by clone and readObject.
    */
    void reinitialize() {
    table = null;
    entrySet = null;
    keySet = null;
    values = null;
    modCount = 0;
    threshold = 0;
    size = 0;
    }

  // Callbacks to allow LinkedHashMap post-actions
  void afterNodeAccess(Node<K,V> p) { }
  void afterNodeInsertion(boolean evict) { }
  void afterNodeRemoval(Node<K,V> p) { }

  // Called only from writeObject, to ensure compatible ordering.
  void internalWriteEntries(java.io.ObjectOutputStream s) throws IOException {
  Node<K,V>[] tab;
  if (size > 0 && (tab = table) != null) {
  for (int i = 0; i < tab.length; ++i) {
  for (Node<K,V> e = tab[i]; e != null; e = e.next) {
  s.writeObject(e.key);
  s.writeObject(e.value);
  }
  }
  }
  }

  /* ------------------------------------------------------------ */
  // Tree bins

  /**

  • Entry for Tree bins. Extends LinkedHashMap.Entry (which in turn

  • extends Node) so can be used as extension of either regular or

  • linked node.
    */
    static final class TreeNode<K,V> extends LinkedHashMap.LinkedHashMapEntry<K,V> {
    TreeNode<K,V> parent; // red-black tree links
    TreeNode<K,V> left;
    TreeNode<K,V> right;
    TreeNode<K,V> prev; // needed to unlink next upon deletion
    boolean red;
    TreeNode(int hash, K key, V val, Node<K,V> next) {
    super(hash, key, val, next);
    }

    /**

    • Returns root of tree containing this node.
      */
      final TreeNode<K,V> root() {
      for (TreeNode<K,V> r = this, p;😉 {
      if ((p = r.parent) == null)
      return r;
      r = p;
      }
      }

    /**

    • Ensures that the given root is the first node of its bin.
      */
      static <K,V> void moveRootToFront(Node<K,V>[] tab, TreeNode<K,V> root) {
      int n;
      if (root != null && tab != null && (n = tab.length) > 0) {
      int index = (n - 1) & root.hash;
      TreeNode<K,V> first = (TreeNode<K,V>)tab[index];
      if (root != first) {
      Node<K,V> rn;
      tab[index] = root;
      TreeNode<K,V> rp = root.prev;
      if ((rn = root.next) != null)
      ((TreeNode<K,V>)rn).prev = rp;
      if (rp != null)
      rp.next = rn;
      if (first != null)
      first.prev = root;
      root.next = first;
      root.prev = null;
      }
      assert checkInvariants(root);
      }
      }

    /**

    • Finds the node starting at root p with the given hash and key.
    • The kc argument caches comparableClassFor(key) upon first use
    • comparing keys.
      */
      final TreeNode<K,V> find(int h, Object k, Class<?> kc) {
      TreeNode<K,V> p = this;
      do {
      int ph, dir; K pk;
      TreeNode<K,V> pl = p.left, pr = p.right, q;
      if ((ph = p.hash) > h)
      p = pl;
      else if (ph < h)
      p = pr;
      else if ((pk = p.key) == k || (k != null && k.equals(pk)))
      return p;
      else if (pl == null)
      p = pr;
      else if (pr == null)
      p = pl;
      else if ((kc != null ||
      (kc = comparableClassFor(k)) != null) &&
      (dir = compareComparables(kc, k, pk)) != 0)
      p = (dir < 0) ? pl : pr;
      else if ((q = pr.find(h, k, kc)) != null)
      return q;
      else
      p = pl;
      } while (p != null);
      return null;
      }

    /**

    • Calls find for root node.
      */
      final TreeNode<K,V> getTreeNode(int h, Object k) {
      return ((parent != null) ? root() : this).find(h, k, null);
      }

    /**

    • Tie-breaking utility for ordering insertions when equal
    • hashCodes and non-comparable. We don’t require a total
    • order, just a consistent insertion rule to maintain
    • equivalence across rebalancings. Tie-breaking further than
    • necessary simplifies testing a bit.
      */
      static int tieBreakOrder(Object a, Object b) {
      int d;
      if (a == null || b == null ||
      (d = a.getClass().getName().
      compareTo(b.getClass().getName())) == 0)
      d = (System.identityHashCode(a) <= System.identityHashCode(b) ?
      -1 : 1);
      return d;
      }

    /**

    • Forms tree of the nodes linked from this node.

    • @return root of tree
      */
      final void treeify(Node<K,V>[] tab) {
      TreeNode<K,V> root = null;
      for (TreeNode<K,V> x = this, next; x != null; x = next) {
      next = (TreeNode<K,V>)x.next;
      x.left = x.right = null;
      if (root == null) {
      x.parent = null;
      x.red = false;
      root = x;
      }
      else {
      K k = x.key;
      int h = x.hash;
      Class<?> kc = null;
      for (TreeNode<K,V> p = root;😉 {
      int dir, ph;
      K pk = p.key;
      if ((ph = p.hash) > h)
      dir = -1;
      else if (ph < h)
      dir = 1;
      else if ((kc == null &&
      (kc = comparableClassFor(k)) == null) ||
      (dir = compareComparables(kc, k, pk)) == 0)
      dir = tieBreakOrder(k, pk);

               TreeNode<K,V> xp = p;
               if ((p = (dir <= 0) ? p.left : p.right) == null) {
                   x.parent = xp;
                   if (dir <= 0)
                       xp.left = x;
                   else
                       xp.right = x;
                   root = balanceInsertion(root, x);
                   break;
               }
           }
       }
      

      }
      moveRootToFront(tab, root);
      }

    /**

    • Returns a list of non-TreeNodes replacing those linked from
    • this node.
      */
      final Node<K,V> untreeify(HashMap<K,V> map) {
      Node<K,V> hd = null, tl = null;
      for (Node<K,V> q = this; q != null; q = q.next) {
      Node<K,V> p = map.replacementNode(q, null);
      if (tl == null)
      hd = p;
      else
      tl.next = p;
      tl = p;
      }
      return hd;
      }

    /**

    • Tree version of putVal.
      */
      final TreeNode<K,V> putTreeVal(HashMap<K,V> map, Node<K,V>[] tab,
      int h, K k, V v) {
      Class<?> kc = null;
      boolean searched = false;
      TreeNode<K,V> root = (parent != null) ? root() : this;
      for (TreeNode<K,V> p = root;😉 {
      int dir, ph; K pk;
      if ((ph = p.hash) > h)
      dir = -1;
      else if (ph < h)
      dir = 1;
      else if ((pk = p.key) == k || (k != null && k.equals(pk)))
      return p;
      else if ((kc == null &&
      (kc = comparableClassFor(k)) == null) ||
      (dir = compareComparables(kc, k, pk)) == 0) {
      if (!searched) {
      TreeNode<K,V> q, ch;
      searched = true;
      if (((ch = p.left) != null &&
      (q = ch.find(h, k, kc)) != null) ||
      ((ch = p.right) != null &&
      (q = ch.find(h, k, kc)) != null))
      return q;
      }
      dir = tieBreakOrder(k, pk);
      }

       TreeNode<K,V> xp = p;
       if ((p = (dir <= 0) ? p.left : p.right) == null) {
           Node<K,V> xpn = xp.next;
           TreeNode<K,V> x = map.newTreeNode(h, k, v, xpn);
           if (dir <= 0)
               xp.left = x;
           else
               xp.right = x;
           xp.next = x;
           x.parent = x.prev = xp;
           if (xpn != null)
               ((TreeNode<K,V>)xpn).prev = x;
           moveRootToFront(tab, balanceInsertion(root, x));
           return null;
       }
      

      }
      }

    /**

    • Removes the given node, that must be present before this call.

    • This is messier than typical red-black deletion code because we

    • cannot swap the contents of an interior node with a leaf

    • successor that is pinned by “next” pointers that are accessible

    • independently during traversal. So instead we swap the tree

    • linkages. If the current tree appears to have too few nodes,

    • the bin is converted back to a plain bin. (The test triggers

    • somewhere between 2 and 6 nodes, depending on tree structure).
      */
      final void removeTreeNode(HashMap<K,V> map, Node<K,V>[] tab,
      boolean movable) {
      int n;
      if (tab == null || (n = tab.length) == 0)
      return;
      int index = (n - 1) & hash;
      TreeNode<K,V> first = (TreeNode<K,V>)tab[index], root = first, rl;
      TreeNode<K,V> succ = (TreeNode<K,V>)next, pred = prev;
      if (pred == null)
      tab[index] = first = succ;
      else
      pred.next = succ;
      if (succ != null)
      succ.prev = pred;
      if (first == null)
      return;
      if (root.parent != null)
      root = root.root();
      if (root == null || root.right == null ||
      (rl = root.left) == null || rl.left == null) {
      tab[index] = first.untreeify(map); // too small
      return;
      }
      TreeNode<K,V> p = this, pl = left, pr = right, replacement;
      if (pl != null && pr != null) {
      TreeNode<K,V> s = pr, sl;
      while ((sl = s.left) != null) // find successor
      s = sl;
      boolean c = s.red; s.red = p.red; p.red = c; // swap colors
      TreeNode<K,V> sr = s.right;
      TreeNode<K,V> pp = p.parent;
      if (s == pr) { // p was s’s direct parent
      p.parent = s;
      s.right = p;
      }
      else {
      TreeNode<K,V> sp = s.parent;
      if ((p.parent = sp) != null) {
      if (s == sp.left)
      sp.left = p;
      else
      sp.right = p;
      }
      if ((s.right = pr) != null)
      pr.parent = s;
      }
      p.left = null;
      if ((p.right = sr) != null)
      sr.parent = p;
      if ((s.left = pl) != null)
      pl.parent = s;
      if ((s.parent = pp) == null)
      root = s;
      else if (p == pp.left)
      pp.left = s;
      else
      pp.right = s;
      if (sr != null)
      replacement = sr;
      else
      replacement = p;
      }
      else if (pl != null)
      replacement = pl;
      else if (pr != null)
      replacement = pr;
      else
      replacement = p;
      if (replacement != p) {
      TreeNode<K,V> pp = replacement.parent = p.parent;
      if (pp == null)
      root = replacement;
      else if (p == pp.left)
      pp.left = replacement;
      else
      pp.right = replacement;
      p.left = p.right = p.parent = null;
      }

      TreeNode<K,V> r = p.red ? root : balanceDeletion(root, replacement);

      if (replacement == p) { // detach
      TreeNode<K,V> pp = p.parent;
      p.parent = null;
      if (pp != null) {
      if (p == pp.left)
      pp.left = null;
      else if (p == pp.right)
      pp.right = null;
      }
      }
      if (movable)
      moveRootToFront(tab, r);
      }

    /**

    • Splits nodes in a tree bin into lower and upper tree bins,

    • or untreeifies if now too small. Called only from resize;

    • see above discussion about split bits and indices.

    • @param map the map

    • @param tab the table for recording bin heads

    • @param index the index of the table being split

    • @param bit the bit of hash to split on
      */
      final void split(HashMap<K,V> map, Node<K,V>[] tab, int index, int bit) {
      TreeNode<K,V> b = this;
      // Relink into lo and hi lists, preserving order
      TreeNode<K,V> loHead = null, loTail = null;
      TreeNode<K,V> hiHead = null, hiTail = null;
      int lc = 0, hc = 0;
      for (TreeNode<K,V> e = b, next; e != null; e = next) {
      next = (TreeNode<K,V>)e.next;
      e.next = null;
      if ((e.hash & bit) == 0) {
      if ((e.prev = loTail) == null)
      loHead = e;
      else
      loTail.next = e;
      loTail = e;
      ++lc;
      }
      else {
      if ((e.prev = hiTail) == null)
      hiHead = e;
      else
      hiTail.next = e;
      hiTail = e;
      ++hc;
      }
      }

      if (loHead != null) {
      if (lc <= UNTREEIFY_THRESHOLD)
      tab[index] = loHead.untreeify(map);
      else {
      tab[index] = loHead;
      if (hiHead != null) // (else is already treeified)
      loHead.treeify(tab);
      }
      }
      if (hiHead != null) {
      if (hc <= UNTREEIFY_THRESHOLD)
      tab[index + bit] = hiHead.untreeify(map);
      else {
      tab[index + bit] = hiHead;
      if (loHead != null)
      hiHead.treeify(tab);
      }
      }
      }

    /* ------------------------------------------------------------ */
    // Red-black tree methods, all adapted from CLR

    static <K,V> TreeNode<K,V> rotateLeft(TreeNode<K,V> root,
    TreeNode<K,V> p) {
    TreeNode<K,V> r, pp, rl;
    if (p != null && (r = p.right) != null) {
    if ((rl = p.right = r.left) != null)
    rl.parent = p;
    if ((pp = r.parent = p.parent) == null)
    (root = r).red = false;
    else if (pp.left == p)
    pp.left = r;
    else
    pp.right = r;
    r.left = p;
    p.parent = r;
    }
    return root;
    }

    static <K,V> TreeNode<K,V> rotateRight(TreeNode<K,V> root,
    TreeNode<K,V> p) {
    TreeNode<K,V> l, pp, lr;
    if (p != null && (l = p.left) != null) {
    if ((lr = p.left = l.right) != null)
    lr.parent = p;
    if ((pp = l.parent = p.parent) == null)
    (root = l).red = false;
    else if (pp.right == p)
    pp.right = l;
    else
    pp.left = l;
    l.right = p;
    p.parent = l;
    }
    return root;
    }

    static <K,V> TreeNode<K,V> balanceInsertion(TreeNode<K,V> root,
    TreeNode<K,V> x) {
    x.red = true;
    for (TreeNode<K,V> xp, xpp, xppl, xppr;😉 {
    if ((xp = x.parent) == null) {
    x.red = false;
    return x;
    }
    else if (!xp.red || (xpp = xp.parent) == null)
    return root;
    if (xp == (xppl = xpp.left)) {
    if ((xppr = xpp.right) != null && xppr.red) {
    xppr.red = false;
    xp.red = false;
    xpp.red = true;
    x = xpp;
    }
    else {
    if (x == xp.right) {
    root = rotateLeft(root, x = xp);
    xpp = (xp = x.parent) == null ? null : xp.parent;
    }
    if (xp != null) {
    xp.red = false;
    if (xpp != null) {
    xpp.red = true;
    root = rotateRight(root, xpp);
    }
    }
    }
    }
    else {
    if (xppl != null && xppl.red) {
    xppl.red = false;
    xp.red = false;
    xpp.red = true;
    x = xpp;
    }
    else {
    if (x == xp.left) {
    root = rotateRight(root, x = xp);
    xpp = (xp = x.parent) == null ? null : xp.parent;
    }
    if (xp != null) {
    xp.red = false;
    if (xpp != null) {
    xpp.red = true;
    root = rotateLeft(root, xpp);
    }
    }
    }
    }
    }
    }

    static <K,V> TreeNode<K,V> balanceDeletion(TreeNode<K,V> root,
    TreeNode<K,V> x) {
    for (TreeNode<K,V> xp, xpl, xpr;😉 {
    if (x == null || x == root)
    return root;
    else if ((xp = x.parent) == null) {
    x.red = false;
    return x;
    }
    else if (x.red) {
    x.red = false;
    return root;
    }
    else if ((xpl = xp.left) == x) {
    if ((xpr = xp.right) != null && xpr.red) {
    xpr.red = false;
    xp.red = true;
    root = rotateLeft(root, xp);
    xpr = (xp = x.parent) == null ? null : xp.right;
    }
    if (xpr == null)
    x = xp;
    else {
    TreeNode<K,V> sl = xpr.left, sr = xpr.right;
    if ((sr == null || !sr.red) &&
    (sl == null || !sl.red)) {
    xpr.red = true;
    x = xp;
    }
    else {
    if (sr == null || !sr.red) {
    if (sl != null)
    sl.red = false;
    xpr.red = true;
    root = rotateRight(root, xpr);
    xpr = (xp = x.parent) == null ?
    null : xp.right;
    }
    if (xpr != null) {
    xpr.red = (xp == null) ? false : xp.red;
    if ((sr = xpr.right) != null)
    sr.red = false;
    }
    if (xp != null) {
    xp.red = false;
    root = rotateLeft(root, xp);
    }
    x = root;
    }
    }
    }
    else { // symmetric
    if (xpl != null && xpl.red) {
    xpl.red = false;
    xp.red = true;
    root = rotateRight(root, xp);
    xpl = (xp = x.parent) == null ? null : xp.left;
    }
    if (xpl == null)
    x = xp;
    else {
    TreeNode<K,V> sl = xpl.left, sr = xpl.right;
    if ((sl == null || !sl.red) &&
    (sr == null || !sr.red)) {
    xpl.red = true;
    x = xp;
    }
    else {
    if (sl == null || !sl.red) {
    if (sr != null)
    sr.red = false;
    xpl.red = true;
    root = rotateLeft(root, xpl);
    xpl = (xp = x.parent) == null ?
    null : xp.left;
    }
    if (xpl != null) {
    xpl.red = (xp == null) ? false : xp.red;
    if ((sl = xpl.left) != null)
    sl.red = false;
    }
    if (xp != null) {
    xp.red = false;
    root = rotateRight(root, xp);
    }
    x = root;
    }
    }
    }
    }
    }

    /**

    • Recursive invariant check
      */
      static <K,V> boolean checkInvariants(TreeNode<K,V> t) {
      TreeNode<K,V> tp = t.parent, tl = t.left, tr = t.right,
      tb = t.prev, tn = (TreeNode<K,V>)t.next;
      if (tb != null && tb.next != t)
      return false;
      if (tn != null && tn.prev != t)
      return false;
      if (tp != null && t != tp.left && t != tp.right)
      return false;
      if (tl != null && (tl.parent != t || tl.hash > t.hash))
      return false;
      if (tr != null && (tr.parent != t || tr.hash < t.hash))
      return false;
      if (t.red && tl != null && tl.red && tr != null && tr.red)
      return false;
      if (tl != null && !checkInvariants(tl))
      return false;
      if (tr != null && !checkInvariants(tr))
      return false;
      return true;
      }
      }

}

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