Automatic sources dropoff on 2020-06-10 18:32:38.095721
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Change-Id: I24cbf6ba6db262a1ae1445db1427a08fee35b3b4
diff --git a/java/util/Hashtable.java b/java/util/Hashtable.java
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+/*
+ * Copyright (C) 2014 The Android Open Source Project
+ * Copyright (c) 1994, 2013, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation. Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+package java.util;
+
+import java.io.*;
+import java.util.function.BiConsumer;
+import java.util.function.BiFunction;
+import java.util.function.Function;
+
+/**
+ * This class implements a hash table, which maps keys to values. Any
+ * non-<code>null</code> object can be used as a key or as a value. <p>
+ *
+ * To successfully store and retrieve objects from a hashtable, the
+ * objects used as keys must implement the <code>hashCode</code>
+ * method and the <code>equals</code> method. <p>
+ *
+ * An instance of <code>Hashtable</code> has two parameters that affect its
+ * performance: <i>initial capacity</i> and <i>load factor</i>. The
+ * <i>capacity</i> is the number of <i>buckets</i> in the hash table, and the
+ * <i>initial capacity</i> is simply the capacity at the time the hash table
+ * is created. Note that the hash table is <i>open</i>: in the case of a "hash
+ * collision", a single bucket stores multiple entries, which must be searched
+ * sequentially. The <i>load factor</i> is a measure of how full the hash
+ * table is allowed to get before its capacity is automatically increased.
+ * The initial capacity and load factor parameters are merely hints to
+ * the implementation. The exact details as to when and whether the rehash
+ * method is invoked are implementation-dependent.<p>
+ *
+ * Generally, the default load factor (.75) offers a good tradeoff between
+ * time and space costs. Higher values decrease the space overhead but
+ * increase the time cost to look up an entry (which is reflected in most
+ * <tt>Hashtable</tt> operations, including <tt>get</tt> and <tt>put</tt>).<p>
+ *
+ * The initial capacity controls a tradeoff between wasted space and the
+ * need for <code>rehash</code> operations, which are time-consuming.
+ * No <code>rehash</code> operations will <i>ever</i> occur if the initial
+ * capacity is greater than the maximum number of entries the
+ * <tt>Hashtable</tt> will contain divided by its load factor. However,
+ * setting the initial capacity too high can waste space.<p>
+ *
+ * If many entries are to be made into a <code>Hashtable</code>,
+ * creating it with a sufficiently large capacity may allow the
+ * entries to be inserted more efficiently than letting it perform
+ * automatic rehashing as needed to grow the table. <p>
+ *
+ * This example creates a hashtable of numbers. It uses the names of
+ * the numbers as keys:
+ * <pre> {@code
+ * Hashtable<String, Integer> numbers
+ * = new Hashtable<String, Integer>();
+ * numbers.put("one", 1);
+ * numbers.put("two", 2);
+ * numbers.put("three", 3);}</pre>
+ *
+ * <p>To retrieve a number, use the following code:
+ * <pre> {@code
+ * Integer n = numbers.get("two");
+ * if (n != null) {
+ * System.out.println("two = " + n);
+ * }}</pre>
+ *
+ * <p>The iterators returned by the <tt>iterator</tt> method of the collections
+ * returned by all of this class's "collection view methods" are
+ * <em>fail-fast</em>: if the Hashtable is structurally modified at any time
+ * after the iterator is created, in any way except through the iterator's own
+ * <tt>remove</tt> 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.
+ * The Enumerations returned by Hashtable's keys and elements methods are
+ * <em>not</em> fail-fast.
+ *
+ * <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 <tt>ConcurrentModificationException</tt> 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>As of the Java 2 platform v1.2, this class was retrofitted to
+ * implement the {@link Map} interface, making it a member of the
+ * <a href="{@docRoot}/../technotes/guides/collections/index.html">
+ *
+ * Java Collections Framework</a>. Unlike the new collection
+ * implementations, {@code Hashtable} is synchronized. If a
+ * thread-safe implementation is not needed, it is recommended to use
+ * {@link HashMap} in place of {@code Hashtable}. If a thread-safe
+ * highly-concurrent implementation is desired, then it is recommended
+ * to use {@link java.util.concurrent.ConcurrentHashMap} in place of
+ * {@code Hashtable}.
+ *
+ * @author Arthur van Hoff
+ * @author Josh Bloch
+ * @author Neal Gafter
+ * @see Object#equals(java.lang.Object)
+ * @see Object#hashCode()
+ * @see Hashtable#rehash()
+ * @see Collection
+ * @see Map
+ * @see HashMap
+ * @see TreeMap
+ * @since JDK1.0
+ */
+public class Hashtable<K,V>
+ extends Dictionary<K,V>
+ implements Map<K,V>, Cloneable, java.io.Serializable {
+
+ /**
+ * The hash table data.
+ */
+ private transient HashtableEntry<?,?>[] table;
+
+ /**
+ * The total number of entries in the hash table.
+ */
+ private transient int count;
+
+ /**
+ * The table is rehashed when its size exceeds this threshold. (The
+ * value of this field is (int)(capacity * loadFactor).)
+ *
+ * @serial
+ */
+ private int threshold;
+
+ /**
+ * The load factor for the hashtable.
+ *
+ * @serial
+ */
+ private float loadFactor;
+
+ /**
+ * The number of times this Hashtable has been structurally modified
+ * Structural modifications are those that change the number of entries in
+ * the Hashtable or otherwise modify its internal structure (e.g.,
+ * rehash). This field is used to make iterators on Collection-views of
+ * the Hashtable fail-fast. (See ConcurrentModificationException).
+ */
+ private transient int modCount = 0;
+
+ /** use serialVersionUID from JDK 1.0.2 for interoperability */
+ private static final long serialVersionUID = 1421746759512286392L;
+
+ /**
+ * Constructs a new, empty hashtable with the specified initial
+ * capacity and the specified load factor.
+ *
+ * @param initialCapacity the initial capacity of the hashtable.
+ * @param loadFactor the load factor of the hashtable.
+ * @exception IllegalArgumentException if the initial capacity is less
+ * than zero, or if the load factor is nonpositive.
+ */
+ public Hashtable(int initialCapacity, float loadFactor) {
+ if (initialCapacity < 0)
+ throw new IllegalArgumentException("Illegal Capacity: "+
+ initialCapacity);
+ if (loadFactor <= 0 || Float.isNaN(loadFactor))
+ throw new IllegalArgumentException("Illegal Load: "+loadFactor);
+
+ if (initialCapacity==0)
+ initialCapacity = 1;
+ this.loadFactor = loadFactor;
+ table = new HashtableEntry<?,?>[initialCapacity];
+ // Android-changed: Ignore loadFactor when calculating threshold from initialCapacity
+ // threshold = (int)Math.min(initialCapacity * loadFactor, MAX_ARRAY_SIZE + 1);
+ threshold = (int)Math.min(initialCapacity, MAX_ARRAY_SIZE + 1);
+ }
+
+ /**
+ * Constructs a new, empty hashtable with the specified initial capacity
+ * and default load factor (0.75).
+ *
+ * @param initialCapacity the initial capacity of the hashtable.
+ * @exception IllegalArgumentException if the initial capacity is less
+ * than zero.
+ */
+ public Hashtable(int initialCapacity) {
+ this(initialCapacity, 0.75f);
+ }
+
+ /**
+ * Constructs a new, empty hashtable with a default initial capacity (11)
+ * and load factor (0.75).
+ */
+ public Hashtable() {
+ this(11, 0.75f);
+ }
+
+ /**
+ * Constructs a new hashtable with the same mappings as the given
+ * Map. The hashtable is created with an initial capacity sufficient to
+ * hold the mappings in the given Map and a default load factor (0.75).
+ *
+ * @param t the map whose mappings are to be placed in this map.
+ * @throws NullPointerException if the specified map is null.
+ * @since 1.2
+ */
+ public Hashtable(Map<? extends K, ? extends V> t) {
+ this(Math.max(2*t.size(), 11), 0.75f);
+ putAll(t);
+ }
+
+ /**
+ * Returns the number of keys in this hashtable.
+ *
+ * @return the number of keys in this hashtable.
+ */
+ public synchronized int size() {
+ return count;
+ }
+
+ /**
+ * Tests if this hashtable maps no keys to values.
+ *
+ * @return <code>true</code> if this hashtable maps no keys to values;
+ * <code>false</code> otherwise.
+ */
+ public synchronized boolean isEmpty() {
+ return count == 0;
+ }
+
+ /**
+ * Returns an enumeration of the keys in this hashtable.
+ *
+ * @return an enumeration of the keys in this hashtable.
+ * @see Enumeration
+ * @see #elements()
+ * @see #keySet()
+ * @see Map
+ */
+ public synchronized Enumeration<K> keys() {
+ return this.<K>getEnumeration(KEYS);
+ }
+
+ /**
+ * Returns an enumeration of the values in this hashtable.
+ * Use the Enumeration methods on the returned object to fetch the elements
+ * sequentially.
+ *
+ * @return an enumeration of the values in this hashtable.
+ * @see java.util.Enumeration
+ * @see #keys()
+ * @see #values()
+ * @see Map
+ */
+ public synchronized Enumeration<V> elements() {
+ return this.<V>getEnumeration(VALUES);
+ }
+
+ /**
+ * Tests if some key maps into the specified value in this hashtable.
+ * This operation is more expensive than the {@link #containsKey
+ * containsKey} method.
+ *
+ * <p>Note that this method is identical in functionality to
+ * {@link #containsValue containsValue}, (which is part of the
+ * {@link Map} interface in the collections framework).
+ *
+ * @param value a value to search for
+ * @return <code>true</code> if and only if some key maps to the
+ * <code>value</code> argument in this hashtable as
+ * determined by the <tt>equals</tt> method;
+ * <code>false</code> otherwise.
+ * @exception NullPointerException if the value is <code>null</code>
+ */
+ public synchronized boolean contains(Object value) {
+ if (value == null) {
+ throw new NullPointerException();
+ }
+
+ HashtableEntry<?,?> tab[] = table;
+ for (int i = tab.length ; i-- > 0 ;) {
+ for (HashtableEntry<?,?> e = tab[i] ; e != null ; e = e.next) {
+ if (e.value.equals(value)) {
+ return true;
+ }
+ }
+ }
+ return false;
+ }
+
+ /**
+ * Returns true if this hashtable maps one or more keys to this value.
+ *
+ * <p>Note that this method is identical in functionality to {@link
+ * #contains contains} (which predates the {@link Map} interface).
+ *
+ * @param value value whose presence in this hashtable is to be tested
+ * @return <tt>true</tt> if this map maps one or more keys to the
+ * specified value
+ * @throws NullPointerException if the value is <code>null</code>
+ * @since 1.2
+ */
+ public boolean containsValue(Object value) {
+ return contains(value);
+ }
+
+ /**
+ * Tests if the specified object is a key in this hashtable.
+ *
+ * @param key possible key
+ * @return <code>true</code> if and only if the specified object
+ * is a key in this hashtable, as determined by the
+ * <tt>equals</tt> method; <code>false</code> otherwise.
+ * @throws NullPointerException if the key is <code>null</code>
+ * @see #contains(Object)
+ */
+ public synchronized boolean containsKey(Object key) {
+ HashtableEntry<?,?> tab[] = table;
+ int hash = key.hashCode();
+ int index = (hash & 0x7FFFFFFF) % tab.length;
+ for (HashtableEntry<?,?> e = tab[index] ; e != null ; e = e.next) {
+ if ((e.hash == hash) && e.key.equals(key)) {
+ 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.equals(k))},
+ * then this method returns {@code v}; otherwise it returns
+ * {@code null}. (There can be at most one such mapping.)
+ *
+ * @param key the key whose associated value is to be returned
+ * @return the value to which the specified key is mapped, or
+ * {@code null} if this map contains no mapping for the key
+ * @throws NullPointerException if the specified key is null
+ * @see #put(Object, Object)
+ */
+ @SuppressWarnings("unchecked")
+ public synchronized V get(Object key) {
+ HashtableEntry<?,?> tab[] = table;
+ int hash = key.hashCode();
+ int index = (hash & 0x7FFFFFFF) % tab.length;
+ for (HashtableEntry<?,?> e = tab[index] ; e != null ; e = e.next) {
+ if ((e.hash == hash) && e.key.equals(key)) {
+ return (V)e.value;
+ }
+ }
+ return null;
+ }
+
+ /**
+ * The maximum size of array to allocate.
+ * Some VMs reserve some header words in an array.
+ * Attempts to allocate larger arrays may result in
+ * OutOfMemoryError: Requested array size exceeds VM limit
+ */
+ private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
+
+ /**
+ * Increases the capacity of and internally reorganizes this
+ * hashtable, in order to accommodate and access its entries more
+ * efficiently. This method is called automatically when the
+ * number of keys in the hashtable exceeds this hashtable's capacity
+ * and load factor.
+ */
+ @SuppressWarnings("unchecked")
+ protected void rehash() {
+ int oldCapacity = table.length;
+ HashtableEntry<?,?>[] oldMap = table;
+
+ // overflow-conscious code
+ int newCapacity = (oldCapacity << 1) + 1;
+ if (newCapacity - MAX_ARRAY_SIZE > 0) {
+ if (oldCapacity == MAX_ARRAY_SIZE)
+ // Keep running with MAX_ARRAY_SIZE buckets
+ return;
+ newCapacity = MAX_ARRAY_SIZE;
+ }
+ HashtableEntry<?,?>[] newMap = new HashtableEntry<?,?>[newCapacity];
+
+ modCount++;
+ threshold = (int)Math.min(newCapacity * loadFactor, MAX_ARRAY_SIZE + 1);
+ table = newMap;
+
+ for (int i = oldCapacity ; i-- > 0 ;) {
+ for (HashtableEntry<K,V> old = (HashtableEntry<K,V>)oldMap[i] ; old != null ; ) {
+ HashtableEntry<K,V> e = old;
+ old = old.next;
+
+ int index = (e.hash & 0x7FFFFFFF) % newCapacity;
+ e.next = (HashtableEntry<K,V>)newMap[index];
+ newMap[index] = e;
+ }
+ }
+ }
+
+ private void addEntry(int hash, K key, V value, int index) {
+ modCount++;
+
+ HashtableEntry<?,?> tab[] = table;
+ if (count >= threshold) {
+ // Rehash the table if the threshold is exceeded
+ rehash();
+
+ tab = table;
+ hash = key.hashCode();
+ index = (hash & 0x7FFFFFFF) % tab.length;
+ }
+
+ // Creates the new entry.
+ @SuppressWarnings("unchecked")
+ HashtableEntry<K,V> e = (HashtableEntry<K,V>) tab[index];
+ tab[index] = new HashtableEntry<>(hash, key, value, e);
+ count++;
+ }
+
+ /**
+ * Maps the specified <code>key</code> to the specified
+ * <code>value</code> in this hashtable. Neither the key nor the
+ * value can be <code>null</code>. <p>
+ *
+ * The value can be retrieved by calling the <code>get</code> method
+ * with a key that is equal to the original key.
+ *
+ * @param key the hashtable key
+ * @param value the value
+ * @return the previous value of the specified key in this hashtable,
+ * or <code>null</code> if it did not have one
+ * @exception NullPointerException if the key or value is
+ * <code>null</code>
+ * @see Object#equals(Object)
+ * @see #get(Object)
+ */
+ public synchronized V put(K key, V value) {
+ // Make sure the value is not null
+ if (value == null) {
+ throw new NullPointerException();
+ }
+
+ // Makes sure the key is not already in the hashtable.
+ HashtableEntry<?,?> tab[] = table;
+ int hash = key.hashCode();
+ int index = (hash & 0x7FFFFFFF) % tab.length;
+ @SuppressWarnings("unchecked")
+ HashtableEntry<K,V> entry = (HashtableEntry<K,V>)tab[index];
+ for(; entry != null ; entry = entry.next) {
+ if ((entry.hash == hash) && entry.key.equals(key)) {
+ V old = entry.value;
+ entry.value = value;
+ return old;
+ }
+ }
+
+ addEntry(hash, key, value, index);
+ return null;
+ }
+
+ /**
+ * Removes the key (and its corresponding value) from this
+ * hashtable. This method does nothing if the key is not in the hashtable.
+ *
+ * @param key the key that needs to be removed
+ * @return the value to which the key had been mapped in this hashtable,
+ * or <code>null</code> if the key did not have a mapping
+ * @throws NullPointerException if the key is <code>null</code>
+ */
+ public synchronized V remove(Object key) {
+ HashtableEntry<?,?> tab[] = table;
+ int hash = key.hashCode();
+ int index = (hash & 0x7FFFFFFF) % tab.length;
+ @SuppressWarnings("unchecked")
+ HashtableEntry<K,V> e = (HashtableEntry<K,V>)tab[index];
+ for(HashtableEntry<K,V> prev = null ; e != null ; prev = e, e = e.next) {
+ if ((e.hash == hash) && e.key.equals(key)) {
+ modCount++;
+ if (prev != null) {
+ prev.next = e.next;
+ } else {
+ tab[index] = e.next;
+ }
+ count--;
+ V oldValue = e.value;
+ e.value = null;
+ return oldValue;
+ }
+ }
+ return null;
+ }
+
+ /**
+ * Copies all of the mappings from the specified map to this hashtable.
+ * These mappings will replace any mappings that this hashtable had for any
+ * of the keys currently in the specified map.
+ *
+ * @param t mappings to be stored in this map
+ * @throws NullPointerException if the specified map is null
+ * @since 1.2
+ */
+ public synchronized void putAll(Map<? extends K, ? extends V> t) {
+ for (Map.Entry<? extends K, ? extends V> e : t.entrySet())
+ put(e.getKey(), e.getValue());
+ }
+
+ /**
+ * Clears this hashtable so that it contains no keys.
+ */
+ public synchronized void clear() {
+ HashtableEntry<?,?> tab[] = table;
+ modCount++;
+ for (int index = tab.length; --index >= 0; )
+ tab[index] = null;
+ count = 0;
+ }
+
+ /**
+ * Creates a shallow copy of this hashtable. All the structure of the
+ * hashtable itself is copied, but the keys and values are not cloned.
+ * This is a relatively expensive operation.
+ *
+ * @return a clone of the hashtable
+ */
+ public synchronized Object clone() {
+ try {
+ Hashtable<?,?> t = (Hashtable<?,?>)super.clone();
+ t.table = new HashtableEntry<?,?>[table.length];
+ for (int i = table.length ; i-- > 0 ; ) {
+ t.table[i] = (table[i] != null)
+ ? (HashtableEntry<?,?>) table[i].clone() : null;
+ }
+ t.keySet = null;
+ t.entrySet = null;
+ t.values = null;
+ t.modCount = 0;
+ return t;
+ } catch (CloneNotSupportedException e) {
+ // this shouldn't happen, since we are Cloneable
+ throw new InternalError(e);
+ }
+ }
+
+ /**
+ * Returns a string representation of this <tt>Hashtable</tt> object
+ * in the form of a set of entries, enclosed in braces and separated
+ * by the ASCII characters "<tt>, </tt>" (comma and space). Each
+ * entry is rendered as the key, an equals sign <tt>=</tt>, and the
+ * associated element, where the <tt>toString</tt> method is used to
+ * convert the key and element to strings.
+ *
+ * @return a string representation of this hashtable
+ */
+ public synchronized String toString() {
+ int max = size() - 1;
+ if (max == -1)
+ return "{}";
+
+ StringBuilder sb = new StringBuilder();
+ Iterator<Map.Entry<K,V>> it = entrySet().iterator();
+
+ sb.append('{');
+ for (int i = 0; ; i++) {
+ Map.Entry<K,V> e = it.next();
+ K key = e.getKey();
+ V value = e.getValue();
+ sb.append(key == this ? "(this Map)" : key.toString());
+ sb.append('=');
+ sb.append(value == this ? "(this Map)" : value.toString());
+
+ if (i == max)
+ return sb.append('}').toString();
+ sb.append(", ");
+ }
+ }
+
+
+ private <T> Enumeration<T> getEnumeration(int type) {
+ if (count == 0) {
+ return Collections.emptyEnumeration();
+ } else {
+ return new Enumerator<>(type, false);
+ }
+ }
+
+ private <T> Iterator<T> getIterator(int type) {
+ if (count == 0) {
+ return Collections.emptyIterator();
+ } else {
+ return new Enumerator<>(type, true);
+ }
+ }
+
+ // Views
+
+ /**
+ * Each of these fields are initialized to contain an instance of the
+ * appropriate view the first time this view is requested. The views are
+ * stateless, so there's no reason to create more than one of each.
+ */
+ private transient volatile Set<K> keySet;
+ private transient volatile Set<Map.Entry<K,V>> entrySet;
+ private transient volatile Collection<V> values;
+
+ /**
+ * 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 <tt>remove</tt> operation), the results of
+ * the iteration are undefined. The set supports element removal,
+ * which removes the corresponding mapping from the map, via the
+ * <tt>Iterator.remove</tt>, <tt>Set.remove</tt>,
+ * <tt>removeAll</tt>, <tt>retainAll</tt>, and <tt>clear</tt>
+ * operations. It does not support the <tt>add</tt> or <tt>addAll</tt>
+ * operations.
+ *
+ * @since 1.2
+ */
+ public Set<K> keySet() {
+ if (keySet == null)
+ keySet = Collections.synchronizedSet(new KeySet(), this);
+ return keySet;
+ }
+
+ private class KeySet extends AbstractSet<K> {
+ public Iterator<K> iterator() {
+ return getIterator(KEYS);
+ }
+ public int size() {
+ return count;
+ }
+ public boolean contains(Object o) {
+ return containsKey(o);
+ }
+ public boolean remove(Object o) {
+ return Hashtable.this.remove(o) != null;
+ }
+ public void clear() {
+ Hashtable.this.clear();
+ }
+ }
+
+ /**
+ * 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 <tt>remove</tt> operation, or through the
+ * <tt>setValue</tt> 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 <tt>Iterator.remove</tt>,
+ * <tt>Set.remove</tt>, <tt>removeAll</tt>, <tt>retainAll</tt> and
+ * <tt>clear</tt> operations. It does not support the
+ * <tt>add</tt> or <tt>addAll</tt> operations.
+ *
+ * @since 1.2
+ */
+ public Set<Map.Entry<K,V>> entrySet() {
+ if (entrySet==null)
+ entrySet = Collections.synchronizedSet(new EntrySet(), this);
+ return entrySet;
+ }
+
+ private class EntrySet extends AbstractSet<Map.Entry<K,V>> {
+ public Iterator<Map.Entry<K,V>> iterator() {
+ return getIterator(ENTRIES);
+ }
+
+ public boolean add(Map.Entry<K,V> o) {
+ return super.add(o);
+ }
+
+ public boolean contains(Object o) {
+ if (!(o instanceof Map.Entry))
+ return false;
+ Map.Entry<?,?> entry = (Map.Entry<?,?>)o;
+ Object key = entry.getKey();
+ HashtableEntry<?,?>[] tab = table;
+ int hash = key.hashCode();
+ int index = (hash & 0x7FFFFFFF) % tab.length;
+
+ for (HashtableEntry<?,?> e = tab[index]; e != null; e = e.next)
+ if (e.hash==hash && e.equals(entry))
+ return true;
+ return false;
+ }
+
+ public boolean remove(Object o) {
+ if (!(o instanceof Map.Entry))
+ return false;
+ Map.Entry<?,?> entry = (Map.Entry<?,?>) o;
+ Object key = entry.getKey();
+ HashtableEntry<?,?>[] tab = table;
+ int hash = key.hashCode();
+ int index = (hash & 0x7FFFFFFF) % tab.length;
+
+ @SuppressWarnings("unchecked")
+ HashtableEntry<K,V> e = (HashtableEntry<K,V>)tab[index];
+ for(HashtableEntry<K,V> prev = null; e != null; prev = e, e = e.next) {
+ if (e.hash==hash && e.equals(entry)) {
+ modCount++;
+ if (prev != null)
+ prev.next = e.next;
+ else
+ tab[index] = e.next;
+
+ count--;
+ e.value = null;
+ return true;
+ }
+ }
+ return false;
+ }
+
+ public int size() {
+ return count;
+ }
+
+ public void clear() {
+ Hashtable.this.clear();
+ }
+ }
+
+ /**
+ * 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 <tt>remove</tt> operation),
+ * the results of the iteration are undefined. The collection
+ * supports element removal, which removes the corresponding
+ * mapping from the map, via the <tt>Iterator.remove</tt>,
+ * <tt>Collection.remove</tt>, <tt>removeAll</tt>,
+ * <tt>retainAll</tt> and <tt>clear</tt> operations. It does not
+ * support the <tt>add</tt> or <tt>addAll</tt> operations.
+ *
+ * @since 1.2
+ */
+ public Collection<V> values() {
+ if (values==null)
+ values = Collections.synchronizedCollection(new ValueCollection(),
+ this);
+ return values;
+ }
+
+ private class ValueCollection extends AbstractCollection<V> {
+ public Iterator<V> iterator() {
+ return getIterator(VALUES);
+ }
+ public int size() {
+ return count;
+ }
+ public boolean contains(Object o) {
+ return containsValue(o);
+ }
+ public void clear() {
+ Hashtable.this.clear();
+ }
+ }
+
+ // Comparison and hashing
+
+ /**
+ * Compares the specified Object with this Map for equality,
+ * as per the definition in the Map interface.
+ *
+ * @param o object to be compared for equality with this hashtable
+ * @return true if the specified Object is equal to this Map
+ * @see Map#equals(Object)
+ * @since 1.2
+ */
+ public synchronized boolean equals(Object o) {
+ if (o == this)
+ return true;
+
+ if (!(o instanceof Map))
+ return false;
+ Map<?,?> t = (Map<?,?>) o;
+ if (t.size() != size())
+ return false;
+
+ try {
+ Iterator<Map.Entry<K,V>> i = entrySet().iterator();
+ while (i.hasNext()) {
+ Map.Entry<K,V> e = i.next();
+ K key = e.getKey();
+ V value = e.getValue();
+ if (value == null) {
+ if (!(t.get(key)==null && t.containsKey(key)))
+ return false;
+ } else {
+ if (!value.equals(t.get(key)))
+ return false;
+ }
+ }
+ } catch (ClassCastException unused) {
+ return false;
+ } catch (NullPointerException unused) {
+ return false;
+ }
+
+ return true;
+ }
+
+ /**
+ * Returns the hash code value for this Map as per the definition in the
+ * Map interface.
+ *
+ * @see Map#hashCode()
+ * @since 1.2
+ */
+ public synchronized int hashCode() {
+ /*
+ * This code detects the recursion caused by computing the hash code
+ * of a self-referential hash table and prevents the stack overflow
+ * that would otherwise result. This allows certain 1.1-era
+ * applets with self-referential hash tables to work. This code
+ * abuses the loadFactor field to do double-duty as a hashCode
+ * in progress flag, so as not to worsen the space performance.
+ * A negative load factor indicates that hash code computation is
+ * in progress.
+ */
+ int h = 0;
+ if (count == 0 || loadFactor < 0)
+ return h; // Returns zero
+
+ loadFactor = -loadFactor; // Mark hashCode computation in progress
+ HashtableEntry<?,?>[] tab = table;
+ for (HashtableEntry<?,?> entry : tab) {
+ while (entry != null) {
+ h += entry.hashCode();
+ entry = entry.next;
+ }
+ }
+
+ loadFactor = -loadFactor; // Mark hashCode computation complete
+
+ return h;
+ }
+
+ @Override
+ public synchronized V getOrDefault(Object key, V defaultValue) {
+ V result = get(key);
+ return (null == result) ? defaultValue : result;
+ }
+
+ @SuppressWarnings("unchecked")
+ @Override
+ public synchronized void forEach(BiConsumer<? super K, ? super V> action) {
+ Objects.requireNonNull(action); // explicit check required in case
+ // table is empty.
+ final int expectedModCount = modCount;
+
+ HashtableEntry<?, ?>[] tab = table;
+ for (HashtableEntry<?, ?> entry : tab) {
+ while (entry != null) {
+ action.accept((K)entry.key, (V)entry.value);
+ entry = entry.next;
+
+ if (expectedModCount != modCount) {
+ throw new ConcurrentModificationException();
+ }
+ }
+ }
+ }
+
+ @SuppressWarnings("unchecked")
+ @Override
+ public synchronized void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) {
+ Objects.requireNonNull(function); // explicit check required in case
+ // table is empty.
+ final int expectedModCount = modCount;
+
+ HashtableEntry<K, V>[] tab = (HashtableEntry<K, V>[])table;
+ for (HashtableEntry<K, V> entry : tab) {
+ while (entry != null) {
+ entry.value = Objects.requireNonNull(
+ function.apply(entry.key, entry.value));
+ entry = entry.next;
+
+ if (expectedModCount != modCount) {
+ throw new ConcurrentModificationException();
+ }
+ }
+ }
+ }
+
+ @Override
+ public synchronized V putIfAbsent(K key, V value) {
+ Objects.requireNonNull(value);
+
+ // Makes sure the key is not already in the hashtable.
+ HashtableEntry<?,?> tab[] = table;
+ int hash = key.hashCode();
+ int index = (hash & 0x7FFFFFFF) % tab.length;
+ @SuppressWarnings("unchecked")
+ HashtableEntry<K,V> entry = (HashtableEntry<K,V>)tab[index];
+ for (; entry != null; entry = entry.next) {
+ if ((entry.hash == hash) && entry.key.equals(key)) {
+ V old = entry.value;
+ if (old == null) {
+ entry.value = value;
+ }
+ return old;
+ }
+ }
+
+ addEntry(hash, key, value, index);
+ return null;
+ }
+
+ @Override
+ public synchronized boolean remove(Object key, Object value) {
+ Objects.requireNonNull(value);
+
+ HashtableEntry<?,?> tab[] = table;
+ int hash = key.hashCode();
+ int index = (hash & 0x7FFFFFFF) % tab.length;
+ @SuppressWarnings("unchecked")
+ HashtableEntry<K,V> e = (HashtableEntry<K,V>)tab[index];
+ for (HashtableEntry<K,V> prev = null; e != null; prev = e, e = e.next) {
+ if ((e.hash == hash) && e.key.equals(key) && e.value.equals(value)) {
+ modCount++;
+ if (prev != null) {
+ prev.next = e.next;
+ } else {
+ tab[index] = e.next;
+ }
+ count--;
+ e.value = null;
+ return true;
+ }
+ }
+ return false;
+ }
+
+ @Override
+ public synchronized boolean replace(K key, V oldValue, V newValue) {
+ Objects.requireNonNull(oldValue);
+ Objects.requireNonNull(newValue);
+ HashtableEntry<?,?> tab[] = table;
+ int hash = key.hashCode();
+ int index = (hash & 0x7FFFFFFF) % tab.length;
+ @SuppressWarnings("unchecked")
+ HashtableEntry<K,V> e = (HashtableEntry<K,V>)tab[index];
+ for (; e != null; e = e.next) {
+ if ((e.hash == hash) && e.key.equals(key)) {
+ if (e.value.equals(oldValue)) {
+ e.value = newValue;
+ return true;
+ } else {
+ return false;
+ }
+ }
+ }
+ return false;
+ }
+
+ @Override
+ public synchronized V replace(K key, V value) {
+ Objects.requireNonNull(value);
+ HashtableEntry<?,?> tab[] = table;
+ int hash = key.hashCode();
+ int index = (hash & 0x7FFFFFFF) % tab.length;
+ @SuppressWarnings("unchecked")
+ HashtableEntry<K,V> e = (HashtableEntry<K,V>)tab[index];
+ for (; e != null; e = e.next) {
+ if ((e.hash == hash) && e.key.equals(key)) {
+ V oldValue = e.value;
+ e.value = value;
+ return oldValue;
+ }
+ }
+ return null;
+ }
+
+ @Override
+ public synchronized V computeIfAbsent(K key, Function<? super K, ? extends V> mappingFunction) {
+ Objects.requireNonNull(mappingFunction);
+
+ HashtableEntry<?,?> tab[] = table;
+ int hash = key.hashCode();
+ int index = (hash & 0x7FFFFFFF) % tab.length;
+ @SuppressWarnings("unchecked")
+ HashtableEntry<K,V> e = (HashtableEntry<K,V>)tab[index];
+ for (; e != null; e = e.next) {
+ if (e.hash == hash && e.key.equals(key)) {
+ // Hashtable not accept null value
+ return e.value;
+ }
+ }
+
+ V newValue = mappingFunction.apply(key);
+ if (newValue != null) {
+ addEntry(hash, key, newValue, index);
+ }
+
+ return newValue;
+ }
+
+ @Override
+ public synchronized V computeIfPresent(K key, BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
+ Objects.requireNonNull(remappingFunction);
+
+ HashtableEntry<?,?> tab[] = table;
+ int hash = key.hashCode();
+ int index = (hash & 0x7FFFFFFF) % tab.length;
+ @SuppressWarnings("unchecked")
+ HashtableEntry<K,V> e = (HashtableEntry<K,V>)tab[index];
+ for (HashtableEntry<K,V> prev = null; e != null; prev = e, e = e.next) {
+ if (e.hash == hash && e.key.equals(key)) {
+ V newValue = remappingFunction.apply(key, e.value);
+ if (newValue == null) {
+ modCount++;
+ if (prev != null) {
+ prev.next = e.next;
+ } else {
+ tab[index] = e.next;
+ }
+ count--;
+ } else {
+ e.value = newValue;
+ }
+ return newValue;
+ }
+ }
+ return null;
+ }
+
+ @Override
+ public synchronized V compute(K key, BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
+ Objects.requireNonNull(remappingFunction);
+
+ HashtableEntry<?,?> tab[] = table;
+ int hash = key.hashCode();
+ int index = (hash & 0x7FFFFFFF) % tab.length;
+ @SuppressWarnings("unchecked")
+ HashtableEntry<K,V> e = (HashtableEntry<K,V>)tab[index];
+ for (HashtableEntry<K,V> prev = null; e != null; prev = e, e = e.next) {
+ if (e.hash == hash && Objects.equals(e.key, key)) {
+ V newValue = remappingFunction.apply(key, e.value);
+ if (newValue == null) {
+ modCount++;
+ if (prev != null) {
+ prev.next = e.next;
+ } else {
+ tab[index] = e.next;
+ }
+ count--;
+ } else {
+ e.value = newValue;
+ }
+ return newValue;
+ }
+ }
+
+ V newValue = remappingFunction.apply(key, null);
+ if (newValue != null) {
+ addEntry(hash, key, newValue, index);
+ }
+
+ return newValue;
+ }
+
+ @Override
+ public synchronized V merge(K key, V value, BiFunction<? super V, ? super V, ? extends V> remappingFunction) {
+ Objects.requireNonNull(remappingFunction);
+
+ HashtableEntry<?,?> tab[] = table;
+ int hash = key.hashCode();
+ int index = (hash & 0x7FFFFFFF) % tab.length;
+ @SuppressWarnings("unchecked")
+ HashtableEntry<K,V> e = (HashtableEntry<K,V>)tab[index];
+ for (HashtableEntry<K,V> prev = null; e != null; prev = e, e = e.next) {
+ if (e.hash == hash && e.key.equals(key)) {
+ V newValue = remappingFunction.apply(e.value, value);
+ if (newValue == null) {
+ modCount++;
+ if (prev != null) {
+ prev.next = e.next;
+ } else {
+ tab[index] = e.next;
+ }
+ count--;
+ } else {
+ e.value = newValue;
+ }
+ return newValue;
+ }
+ }
+
+ if (value != null) {
+ addEntry(hash, key, value, index);
+ }
+
+ return value;
+ }
+
+ /**
+ * Save the state of the Hashtable to a stream (i.e., serialize it).
+ *
+ * @serialData The <i>capacity</i> of the Hashtable (the length of the
+ * bucket array) is emitted (int), followed by the
+ * <i>size</i> of the Hashtable (the number of key-value
+ * mappings), followed by the key (Object) and value (Object)
+ * for each key-value mapping represented by the Hashtable
+ * The key-value mappings are emitted in no particular order.
+ */
+ private void writeObject(java.io.ObjectOutputStream s)
+ throws IOException {
+ HashtableEntry<Object, Object> entryStack = null;
+
+ synchronized (this) {
+ // Write out the threshold and loadFactor
+ s.defaultWriteObject();
+
+ // Write out the length and count of elements
+ s.writeInt(table.length);
+ s.writeInt(count);
+
+ // Stack copies of the entries in the table
+ for (int index = 0; index < table.length; index++) {
+ HashtableEntry<?,?> entry = table[index];
+
+ while (entry != null) {
+ entryStack =
+ new HashtableEntry<>(0, entry.key, entry.value, entryStack);
+ entry = entry.next;
+ }
+ }
+ }
+
+ // Write out the key/value objects from the stacked entries
+ while (entryStack != null) {
+ s.writeObject(entryStack.key);
+ s.writeObject(entryStack.value);
+ entryStack = entryStack.next;
+ }
+ }
+
+ /**
+ * Reconstitute the Hashtable from a stream (i.e., deserialize it).
+ */
+ private void readObject(java.io.ObjectInputStream s)
+ throws IOException, ClassNotFoundException
+ {
+ // Read in the threshold and loadFactor
+ s.defaultReadObject();
+
+ // Validate loadFactor (ignore threshold - it will be re-computed)
+ if (loadFactor <= 0 || Float.isNaN(loadFactor))
+ throw new StreamCorruptedException("Illegal Load: " + loadFactor);
+
+ // Read the original length of the array and number of elements
+ int origlength = s.readInt();
+ int elements = s.readInt();
+
+ // Validate # of elements
+ if (elements < 0)
+ throw new StreamCorruptedException("Illegal # of Elements: " + elements);
+
+ // Clamp original length to be more than elements / loadFactor
+ // (this is the invariant enforced with auto-growth)
+ origlength = Math.max(origlength, (int)(elements / loadFactor) + 1);
+
+ // Compute new length with a bit of room 5% + 3 to grow but
+ // no larger than the clamped original length. Make the length
+ // odd if it's large enough, this helps distribute the entries.
+ // Guard against the length ending up zero, that's not valid.
+ int length = (int)((elements + elements / 20) / loadFactor) + 3;
+ if (length > elements && (length & 1) == 0)
+ length--;
+ length = Math.min(length, origlength);
+ table = new HashtableEntry<?,?>[length];
+ threshold = (int)Math.min(length * loadFactor, MAX_ARRAY_SIZE + 1);
+ count = 0;
+
+ // Read the number of elements and then all the key/value objects
+ for (; elements > 0; elements--) {
+ @SuppressWarnings("unchecked")
+ K key = (K)s.readObject();
+ @SuppressWarnings("unchecked")
+ V value = (V)s.readObject();
+ // sync is eliminated for performance
+ reconstitutionPut(table, key, value);
+ }
+ }
+
+ /**
+ * The put method used by readObject. This is provided because put
+ * is overridable and should not be called in readObject since the
+ * subclass will not yet be initialized.
+ *
+ * <p>This differs from the regular put method in several ways. No
+ * checking for rehashing is necessary since the number of elements
+ * initially in the table is known. The modCount is not incremented and
+ * there's no synchronization because we are creating a new instance.
+ * Also, no return value is needed.
+ */
+ private void reconstitutionPut(HashtableEntry<?,?>[] tab, K key, V value)
+ throws StreamCorruptedException
+ {
+ if (value == null) {
+ throw new java.io.StreamCorruptedException();
+ }
+ // Makes sure the key is not already in the hashtable.
+ // This should not happen in deserialized version.
+ int hash = key.hashCode();
+ int index = (hash & 0x7FFFFFFF) % tab.length;
+ for (HashtableEntry<?,?> e = tab[index] ; e != null ; e = e.next) {
+ if ((e.hash == hash) && e.key.equals(key)) {
+ throw new java.io.StreamCorruptedException();
+ }
+ }
+ // Creates the new entry.
+ @SuppressWarnings("unchecked")
+ HashtableEntry<K,V> e = (HashtableEntry<K,V>)tab[index];
+ tab[index] = new HashtableEntry<>(hash, key, value, e);
+ count++;
+ }
+
+ /**
+ * Hashtable bucket collision list entry
+ */
+ // BEGIN Android-changed: Renamed Entry -> HashtableEntry.
+ // Code references to "HashTable.Entry" must mean Map.Entry
+ //
+ // This mirrors the corresponding rename of LinkedHashMap's
+ // Entry->LinkedHashMapEntry.
+ //
+ // This is for source compatibility with earlier versions of Android.
+ // Otherwise, it would hide Map.Entry which would break compilation
+ // of code like:
+ //
+ // Hashtable.Entry<K, V> entry = hashtable.entrySet().iterator.next();
+ //
+ // To compile, that code snippet's "HashtableMap.Entry" must
+ // mean java.util.Map.Entry which is the compile time type of
+ // entrySet()'s elements.
+ //
+ private static class HashtableEntry<K,V> implements Map.Entry<K,V> {
+ // END Android-changed: Renamed Entry -> HashtableEntry.
+ final int hash;
+ final K key;
+ V value;
+ HashtableEntry<K,V> next;
+
+ protected HashtableEntry(int hash, K key, V value, HashtableEntry<K,V> next) {
+ this.hash = hash;
+ this.key = key;
+ this.value = value;
+ this.next = next;
+ }
+
+ @SuppressWarnings("unchecked")
+ protected Object clone() {
+ return new HashtableEntry<>(hash, key, value,
+ (next==null ? null : (HashtableEntry<K,V>) next.clone()));
+ }
+
+ // Map.Entry Ops
+
+ public K getKey() {
+ return key;
+ }
+
+ public V getValue() {
+ return value;
+ }
+
+ public V setValue(V value) {
+ if (value == null)
+ throw new NullPointerException();
+
+ V oldValue = this.value;
+ this.value = value;
+ return oldValue;
+ }
+
+ public boolean equals(Object o) {
+ if (!(o instanceof Map.Entry))
+ return false;
+ Map.Entry<?,?> e = (Map.Entry<?,?>)o;
+
+ return (key==null ? e.getKey()==null : key.equals(e.getKey())) &&
+ (value==null ? e.getValue()==null : value.equals(e.getValue()));
+ }
+
+ public int hashCode() {
+ return hash ^ Objects.hashCode(value);
+ }
+
+ public String toString() {
+ return key.toString()+"="+value.toString();
+ }
+ }
+
+ // Types of Enumerations/Iterations
+ private static final int KEYS = 0;
+ private static final int VALUES = 1;
+ private static final int ENTRIES = 2;
+
+ /**
+ * A hashtable enumerator class. This class implements both the
+ * Enumeration and Iterator interfaces, but individual instances
+ * can be created with the Iterator methods disabled. This is necessary
+ * to avoid unintentionally increasing the capabilities granted a user
+ * by passing an Enumeration.
+ */
+ private class Enumerator<T> implements Enumeration<T>, Iterator<T> {
+ HashtableEntry<?,?>[] table = Hashtable.this.table;
+ int index = table.length;
+ HashtableEntry<?,?> entry;
+ HashtableEntry<?,?> lastReturned;
+ int type;
+
+ /**
+ * Indicates whether this Enumerator is serving as an Iterator
+ * or an Enumeration. (true -> Iterator).
+ */
+ boolean iterator;
+
+ /**
+ * The modCount value that the iterator believes that the backing
+ * Hashtable should have. If this expectation is violated, the iterator
+ * has detected concurrent modification.
+ */
+ protected int expectedModCount = modCount;
+
+ Enumerator(int type, boolean iterator) {
+ this.type = type;
+ this.iterator = iterator;
+ }
+
+ public boolean hasMoreElements() {
+ HashtableEntry<?,?> e = entry;
+ int i = index;
+ HashtableEntry<?,?>[] t = table;
+ /* Use locals for faster loop iteration */
+ while (e == null && i > 0) {
+ e = t[--i];
+ }
+ entry = e;
+ index = i;
+ return e != null;
+ }
+
+ @SuppressWarnings("unchecked")
+ public T nextElement() {
+ HashtableEntry<?,?> et = entry;
+ int i = index;
+ HashtableEntry<?,?>[] t = table;
+ /* Use locals for faster loop iteration */
+ while (et == null && i > 0) {
+ et = t[--i];
+ }
+ entry = et;
+ index = i;
+ if (et != null) {
+ HashtableEntry<?,?> e = lastReturned = entry;
+ entry = e.next;
+ return type == KEYS ? (T)e.key : (type == VALUES ? (T)e.value : (T)e);
+ }
+ throw new NoSuchElementException("Hashtable Enumerator");
+ }
+
+ // Iterator methods
+ public boolean hasNext() {
+ return hasMoreElements();
+ }
+
+ public T next() {
+ if (modCount != expectedModCount)
+ throw new ConcurrentModificationException();
+ return nextElement();
+ }
+
+ public void remove() {
+ if (!iterator)
+ throw new UnsupportedOperationException();
+ if (lastReturned == null)
+ throw new IllegalStateException("Hashtable Enumerator");
+ if (modCount != expectedModCount)
+ throw new ConcurrentModificationException();
+
+ synchronized(Hashtable.this) {
+ HashtableEntry<?,?>[] tab = Hashtable.this.table;
+ int index = (lastReturned.hash & 0x7FFFFFFF) % tab.length;
+
+ @SuppressWarnings("unchecked")
+ HashtableEntry<K,V> e = (HashtableEntry<K,V>)tab[index];
+ for(HashtableEntry<K,V> prev = null; e != null; prev = e, e = e.next) {
+ if (e == lastReturned) {
+ modCount++;
+ expectedModCount++;
+ if (prev == null)
+ tab[index] = e.next;
+ else
+ prev.next = e.next;
+ count--;
+ lastReturned = null;
+ return;
+ }
+ }
+ throw new ConcurrentModificationException();
+ }
+ }
+ }
+}
