1341 lines
47 KiB
Java
1341 lines
47 KiB
Java
/*
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* Copyright (c) 1998, 2020, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package java.util;
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import java.lang.ref.WeakReference;
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import java.lang.ref.ReferenceQueue;
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import java.util.function.BiConsumer;
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import java.util.function.BiFunction;
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import java.util.function.Consumer;
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/**
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* Hash table based implementation of the {@code Map} interface, with
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* <em>weak keys</em>.
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* An entry in a {@code WeakHashMap} will automatically be removed when
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* its key is no longer in ordinary use. More precisely, the presence of a
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* mapping for a given key will not prevent the key from being discarded by the
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* garbage collector, that is, made finalizable, finalized, and then reclaimed.
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* When a key has been discarded its entry is effectively removed from the map,
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* so this class behaves somewhat differently from other {@code Map}
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* implementations.
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*
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* <p> Both null values and the null key are supported. This class has
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* performance characteristics similar to those of the {@code HashMap}
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* class, and has the same efficiency parameters of <em>initial capacity</em>
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* and <em>load factor</em>.
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*
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* <p> Like most collection classes, this class is not synchronized.
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* A synchronized {@code WeakHashMap} may be constructed using the
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* {@link Collections#synchronizedMap Collections.synchronizedMap}
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* method.
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*
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* <p> This class is intended primarily for use with key objects whose
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* {@code equals} methods test for object identity using the
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* {@code ==} operator. Once such a key is discarded it can never be
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* recreated, so it is impossible to do a lookup of that key in a
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* {@code WeakHashMap} at some later time and be surprised that its entry
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* has been removed. This class will work perfectly well with key objects
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* whose {@code equals} methods are not based upon object identity, such
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* as {@code String} instances. With such recreatable key objects,
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* however, the automatic removal of {@code WeakHashMap} entries whose
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* keys have been discarded may prove to be confusing.
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*
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* <p> The behavior of the {@code WeakHashMap} class depends in part upon
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* the actions of the garbage collector, so several familiar (though not
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* required) {@code Map} invariants do not hold for this class. Because
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* the garbage collector may discard keys at any time, a
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* {@code WeakHashMap} may behave as though an unknown thread is silently
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* removing entries. In particular, even if you synchronize on a
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* {@code WeakHashMap} instance and invoke none of its mutator methods, it
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* is possible for the {@code size} method to return smaller values over
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* time, for the {@code isEmpty} method to return {@code false} and
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* then {@code true}, for the {@code containsKey} method to return
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* {@code true} and later {@code false} for a given key, for the
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* {@code get} method to return a value for a given key but later return
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* {@code null}, for the {@code put} method to return
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* {@code null} and the {@code remove} method to return
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* {@code false} for a key that previously appeared to be in the map, and
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* for successive examinations of the key set, the value collection, and
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* the entry set to yield successively smaller numbers of elements.
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*
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* <p> Each key object in a {@code WeakHashMap} is stored indirectly as
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* the referent of a weak reference. Therefore a key will automatically be
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* removed only after the weak references to it, both inside and outside of the
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* map, have been cleared by the garbage collector.
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*
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* <p> <strong>Implementation note:</strong> The value objects in a
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* {@code WeakHashMap} are held by ordinary strong references. Thus care
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* should be taken to ensure that value objects do not strongly refer to their
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* own keys, either directly or indirectly, since that will prevent the keys
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* from being discarded. Note that a value object may refer indirectly to its
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* key via the {@code WeakHashMap} itself; that is, a value object may
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* strongly refer to some other key object whose associated value object, in
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* turn, strongly refers to the key of the first value object. If the values
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* in the map do not rely on the map holding strong references to them, one way
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* to deal with this is to wrap values themselves within
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* {@code WeakReferences} before
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* inserting, as in: {@code m.put(key, new WeakReference(value))},
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* and then unwrapping upon each {@code get}.
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*
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* <p>The iterators returned by the {@code iterator} method of the collections
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* returned by all of this class's "collection view methods" are
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* <i>fail-fast</i>: if the map is structurally modified at any time after the
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* iterator is created, in any way except through the iterator's own
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* {@code remove} method, the iterator will throw a {@link
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* ConcurrentModificationException}. Thus, in the face of concurrent
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* modification, the iterator fails quickly and cleanly, rather than risking
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* arbitrary, non-deterministic behavior at an undetermined time in the future.
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*
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* <p>Note that the fail-fast behavior of an iterator cannot be guaranteed
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* as it is, generally speaking, impossible to make any hard guarantees in the
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* presence of unsynchronized concurrent modification. Fail-fast iterators
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* throw {@code ConcurrentModificationException} on a best-effort basis.
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* Therefore, it would be wrong to write a program that depended on this
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* exception for its correctness: <i>the fail-fast behavior of iterators
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* should be used only to detect bugs.</i>
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*
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* <p>This class is a member of the
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* <a href="{@docRoot}/java.base/java/util/package-summary.html#CollectionsFramework">
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* Java Collections Framework</a>.
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*
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* @param <K> the type of keys maintained by this map
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* @param <V> the type of mapped values
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*
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* @author Doug Lea
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* @author Josh Bloch
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* @author Mark Reinhold
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* @since 1.2
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* @see java.util.HashMap
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* @see java.lang.ref.WeakReference
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*/
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public class WeakHashMap<K,V>
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extends AbstractMap<K,V>
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implements Map<K,V> {
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/**
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* The default initial capacity -- MUST be a power of two.
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*/
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private static final int DEFAULT_INITIAL_CAPACITY = 16;
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/**
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* The maximum capacity, used if a higher value is implicitly specified
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* by either of the constructors with arguments.
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* MUST be a power of two <= 1<<30.
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*/
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private static final int MAXIMUM_CAPACITY = 1 << 30;
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/**
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* The load factor used when none specified in constructor.
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*/
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private static final float DEFAULT_LOAD_FACTOR = 0.75f;
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/**
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* The table, resized as necessary. Length MUST Always be a power of two.
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*/
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Entry<K,V>[] table;
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/**
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* The number of key-value mappings contained in this weak hash map.
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*/
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private int size;
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/**
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* The next size value at which to resize (capacity * load factor).
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*/
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private int threshold;
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/**
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* The load factor for the hash table.
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*/
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private final float loadFactor;
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/**
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* Reference queue for cleared WeakEntries
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*/
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private final ReferenceQueue<Object> queue = new ReferenceQueue<>();
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/**
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* The number of times this WeakHashMap has been structurally modified.
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* Structural modifications are those that change the number of
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* mappings in the map or otherwise modify its internal structure
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* (e.g., rehash). This field is used to make iterators on
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* Collection-views of the map fail-fast.
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*
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* @see ConcurrentModificationException
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*/
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int modCount;
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@SuppressWarnings("unchecked")
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private Entry<K,V>[] newTable(int n) {
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return (Entry<K,V>[]) new Entry<?,?>[n];
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}
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/**
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* Constructs a new, empty {@code WeakHashMap} with the given initial
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* capacity and the given load factor.
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*
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* @param initialCapacity The initial capacity of the {@code WeakHashMap}
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* @param loadFactor The load factor of the {@code WeakHashMap}
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* @throws IllegalArgumentException if the initial capacity is negative,
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* or if the load factor is nonpositive.
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*/
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public WeakHashMap(int initialCapacity, float loadFactor) {
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if (initialCapacity < 0)
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throw new IllegalArgumentException("Illegal Initial Capacity: "+
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initialCapacity);
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if (initialCapacity > MAXIMUM_CAPACITY)
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initialCapacity = MAXIMUM_CAPACITY;
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if (loadFactor <= 0 || Float.isNaN(loadFactor))
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throw new IllegalArgumentException("Illegal Load factor: "+
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loadFactor);
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int capacity = 1;
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while (capacity < initialCapacity)
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capacity <<= 1;
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table = newTable(capacity);
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this.loadFactor = loadFactor;
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threshold = (int)(capacity * loadFactor);
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}
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/**
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* Constructs a new, empty {@code WeakHashMap} with the given initial
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* capacity and the default load factor (0.75).
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*
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* @param initialCapacity The initial capacity of the {@code WeakHashMap}
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* @throws IllegalArgumentException if the initial capacity is negative
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*/
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public WeakHashMap(int initialCapacity) {
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this(initialCapacity, DEFAULT_LOAD_FACTOR);
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}
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/**
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* Constructs a new, empty {@code WeakHashMap} with the default initial
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* capacity (16) and load factor (0.75).
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*/
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public WeakHashMap() {
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this(DEFAULT_INITIAL_CAPACITY, DEFAULT_LOAD_FACTOR);
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}
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/**
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* Constructs a new {@code WeakHashMap} with the same mappings as the
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* specified map. The {@code WeakHashMap} is created with the default
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* load factor (0.75) and an initial capacity sufficient to hold the
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* mappings in the specified map.
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*
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* @param m the map whose mappings are to be placed in this map
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* @throws NullPointerException if the specified map is null
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* @since 1.3
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*/
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public WeakHashMap(Map<? extends K, ? extends V> m) {
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this(Math.max((int) ((float)m.size() / DEFAULT_LOAD_FACTOR + 1.0F),
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DEFAULT_INITIAL_CAPACITY),
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DEFAULT_LOAD_FACTOR);
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putAll(m);
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}
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// internal utilities
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/**
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* Value representing null keys inside tables.
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*/
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private static final Object NULL_KEY = new Object();
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/**
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* Use NULL_KEY for key if it is null.
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*/
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private static Object maskNull(Object key) {
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return (key == null) ? NULL_KEY : key;
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}
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/**
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* Returns internal representation of null key back to caller as null.
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*/
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static Object unmaskNull(Object key) {
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return (key == NULL_KEY) ? null : key;
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}
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/**
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* Checks for equality of non-null reference x and possibly-null y. By
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* default uses Object.equals.
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*/
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private boolean matchesKey(Entry<K,V> e, Object key) {
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// check if the given entry refers to the given key without
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// keeping a strong reference to the entry's referent
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if (e.refersTo(key)) return true;
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// then check for equality if the referent is not cleared
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Object k = e.get();
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return k != null && key.equals(k);
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}
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/**
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* Retrieve object hash code and applies a supplemental hash function to the
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* result hash, which defends against poor quality hash functions. This is
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* critical because HashMap uses power-of-two length hash tables, that
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* otherwise encounter collisions for hashCodes that do not differ
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* in lower bits.
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*/
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final int hash(Object k) {
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int h = k.hashCode();
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// This function ensures that hashCodes that differ only by
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// constant multiples at each bit position have a bounded
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// number of collisions (approximately 8 at default load factor).
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h ^= (h >>> 20) ^ (h >>> 12);
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return h ^ (h >>> 7) ^ (h >>> 4);
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}
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/**
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* Returns index for hash code h.
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*/
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private static int indexFor(int h, int length) {
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return h & (length-1);
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}
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/**
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* Expunges stale entries from the table.
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*/
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private void expungeStaleEntries() {
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for (Object x; (x = queue.poll()) != null; ) {
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synchronized (queue) {
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@SuppressWarnings("unchecked")
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Entry<K,V> e = (Entry<K,V>) x;
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int i = indexFor(e.hash, table.length);
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Entry<K,V> prev = table[i];
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Entry<K,V> p = prev;
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while (p != null) {
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Entry<K,V> next = p.next;
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if (p == e) {
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if (prev == e)
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table[i] = next;
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else
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prev.next = next;
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// Must not null out e.next;
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// stale entries may be in use by a HashIterator
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e.value = null; // Help GC
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size--;
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break;
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}
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prev = p;
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p = next;
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}
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}
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}
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}
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/**
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* Returns the table after first expunging stale entries.
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*/
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private Entry<K,V>[] getTable() {
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expungeStaleEntries();
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return table;
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}
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/**
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* Returns the number of key-value mappings in this map.
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* This result is a snapshot, and may not reflect unprocessed
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* entries that will be removed before next attempted access
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* because they are no longer referenced.
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*/
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public int size() {
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if (size == 0)
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return 0;
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expungeStaleEntries();
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return size;
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}
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/**
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* Returns {@code true} if this map contains no key-value mappings.
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* This result is a snapshot, and may not reflect unprocessed
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* entries that will be removed before next attempted access
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* because they are no longer referenced.
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*/
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public boolean isEmpty() {
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return size() == 0;
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}
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/**
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* Returns the value to which the specified key is mapped,
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* or {@code null} if this map contains no mapping for the key.
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*
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* <p>More formally, if this map contains a mapping from a key
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* {@code k} to a value {@code v} such that
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* {@code Objects.equals(key, k)},
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* then this method returns {@code v}; otherwise
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* it returns {@code null}. (There can be at most one such mapping.)
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*
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* <p>A return value of {@code null} does not <i>necessarily</i>
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* indicate that the map contains no mapping for the key; it's also
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* possible that the map explicitly maps the key to {@code null}.
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* The {@link #containsKey containsKey} operation may be used to
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* distinguish these two cases.
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*
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* @see #put(Object, Object)
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*/
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public V get(Object key) {
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Object k = maskNull(key);
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int h = hash(k);
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Entry<K,V>[] tab = getTable();
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int index = indexFor(h, tab.length);
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Entry<K,V> e = tab[index];
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while (e != null) {
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if (e.hash == h && matchesKey(e, k))
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return e.value;
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e = e.next;
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}
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return null;
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}
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/**
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* Returns {@code true} if this map contains a mapping for the
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* specified key.
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*
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* @param key The key whose presence in this map is to be tested
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* @return {@code true} if there is a mapping for {@code key};
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* {@code false} otherwise
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*/
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public boolean containsKey(Object key) {
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return getEntry(key) != null;
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}
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/**
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* Returns the entry associated with the specified key in this map.
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* Returns null if the map contains no mapping for this key.
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*/
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Entry<K,V> getEntry(Object key) {
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Object k = maskNull(key);
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int h = hash(k);
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Entry<K,V>[] tab = getTable();
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int index = indexFor(h, tab.length);
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Entry<K,V> e = tab[index];
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while (e != null && !(e.hash == h && matchesKey(e, k)))
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e = e.next;
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return e;
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}
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/**
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* Associates the specified value with the specified key in this map.
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* If the map previously contained a mapping for this key, the old
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* value is replaced.
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*
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* @param key key with which the specified value is to be associated.
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* @param value value to be associated with the specified key.
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* @return the previous value associated with {@code key}, or
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* {@code null} if there was no mapping for {@code key}.
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* (A {@code null} return can also indicate that the map
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* previously associated {@code null} with {@code key}.)
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*/
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public V put(K key, V value) {
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Object k = maskNull(key);
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int h = hash(k);
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Entry<K,V>[] tab = getTable();
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int i = indexFor(h, tab.length);
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for (Entry<K,V> e = tab[i]; e != null; e = e.next) {
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if (h == e.hash && matchesKey(e, k)) {
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V oldValue = e.value;
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if (value != oldValue)
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e.value = value;
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return oldValue;
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}
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}
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modCount++;
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Entry<K,V> e = tab[i];
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tab[i] = new Entry<>(k, value, queue, h, e);
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if (++size >= threshold)
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resize(tab.length * 2);
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return null;
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}
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|
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/**
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* Rehashes the contents of this map into a new array with a
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* larger capacity. This method is called automatically when the
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* number of keys in this map reaches its threshold.
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*
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* If current capacity is MAXIMUM_CAPACITY, this method does not
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* resize the map, but sets threshold to Integer.MAX_VALUE.
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* This has the effect of preventing future calls.
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*
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* @param newCapacity the new capacity, MUST be a power of two;
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* must be greater than current capacity unless current
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* capacity is MAXIMUM_CAPACITY (in which case value
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* is irrelevant).
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*/
|
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void resize(int newCapacity) {
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Entry<K,V>[] oldTable = getTable();
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int oldCapacity = oldTable.length;
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if (oldCapacity == MAXIMUM_CAPACITY) {
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threshold = Integer.MAX_VALUE;
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return;
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}
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Entry<K,V>[] newTable = newTable(newCapacity);
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transfer(oldTable, newTable);
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table = newTable;
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/*
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* If ignoring null elements and processing ref queue caused massive
|
|
* shrinkage, then restore old table. This should be rare, but avoids
|
|
* unbounded expansion of garbage-filled tables.
|
|
*/
|
|
if (size >= threshold / 2) {
|
|
threshold = (int)(newCapacity * loadFactor);
|
|
} else {
|
|
expungeStaleEntries();
|
|
transfer(newTable, oldTable);
|
|
table = oldTable;
|
|
}
|
|
}
|
|
|
|
/** Transfers all entries from src to dest tables */
|
|
private void transfer(Entry<K,V>[] src, Entry<K,V>[] dest) {
|
|
for (int j = 0; j < src.length; ++j) {
|
|
Entry<K,V> e = src[j];
|
|
src[j] = null;
|
|
while (e != null) {
|
|
Entry<K,V> next = e.next;
|
|
if (e.refersTo(null)) {
|
|
e.next = null; // Help GC
|
|
e.value = null; // " "
|
|
size--;
|
|
} else {
|
|
int i = indexFor(e.hash, dest.length);
|
|
e.next = dest[i];
|
|
dest[i] = e;
|
|
}
|
|
e = next;
|
|
}
|
|
}
|
|
}
|
|
|
|
/**
|
|
* 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) {
|
|
int numKeysToBeAdded = m.size();
|
|
if (numKeysToBeAdded == 0)
|
|
return;
|
|
|
|
/*
|
|
* Expand the map if the map if the number of mappings to be added
|
|
* is greater than or equal to threshold. This is conservative; the
|
|
* obvious condition is (m.size() + size) >= threshold, but this
|
|
* condition could result in a map with twice the appropriate capacity,
|
|
* if the keys to be added overlap with the keys already in this map.
|
|
* By using the conservative calculation, we subject ourself
|
|
* to at most one extra resize.
|
|
*/
|
|
if (numKeysToBeAdded > threshold) {
|
|
int targetCapacity = (int)(numKeysToBeAdded / loadFactor + 1);
|
|
if (targetCapacity > MAXIMUM_CAPACITY)
|
|
targetCapacity = MAXIMUM_CAPACITY;
|
|
int newCapacity = table.length;
|
|
while (newCapacity < targetCapacity)
|
|
newCapacity <<= 1;
|
|
if (newCapacity > table.length)
|
|
resize(newCapacity);
|
|
}
|
|
|
|
for (Map.Entry<? extends K, ? extends V> e : m.entrySet())
|
|
put(e.getKey(), e.getValue());
|
|
}
|
|
|
|
/**
|
|
* Removes the mapping for a key from this weak hash map if it is present.
|
|
* More formally, if this map contains a mapping from key {@code k} to
|
|
* value {@code v} such that <code>(key==null ? k==null :
|
|
* key.equals(k))</code>, that mapping is removed. (The map can contain
|
|
* at most one such mapping.)
|
|
*
|
|
* <p>Returns the value to which this map previously associated the key,
|
|
* or {@code null} if the map contained no mapping for the key. A
|
|
* return value of {@code null} does not <i>necessarily</i> indicate
|
|
* that the map contained no mapping for the key; it's also possible
|
|
* that the map explicitly mapped the key to {@code null}.
|
|
*
|
|
* <p>The map will not contain a mapping for the specified key once the
|
|
* call returns.
|
|
*
|
|
* @param key key whose mapping is to be removed from the map
|
|
* @return the previous value associated with {@code key}, or
|
|
* {@code null} if there was no mapping for {@code key}
|
|
*/
|
|
public V remove(Object key) {
|
|
Object k = maskNull(key);
|
|
int h = hash(k);
|
|
Entry<K,V>[] tab = getTable();
|
|
int i = indexFor(h, tab.length);
|
|
Entry<K,V> prev = tab[i];
|
|
Entry<K,V> e = prev;
|
|
|
|
while (e != null) {
|
|
Entry<K,V> next = e.next;
|
|
if (h == e.hash && matchesKey(e, k)) {
|
|
modCount++;
|
|
size--;
|
|
if (prev == e)
|
|
tab[i] = next;
|
|
else
|
|
prev.next = next;
|
|
return e.value;
|
|
}
|
|
prev = e;
|
|
e = next;
|
|
}
|
|
|
|
return null;
|
|
}
|
|
|
|
/** Special version of remove needed by Entry set */
|
|
boolean removeMapping(Object o) {
|
|
if (!(o instanceof Map.Entry<?, ?> entry))
|
|
return false;
|
|
Entry<K,V>[] tab = getTable();
|
|
Object k = maskNull(entry.getKey());
|
|
int h = hash(k);
|
|
int i = indexFor(h, tab.length);
|
|
Entry<K,V> prev = tab[i];
|
|
Entry<K,V> e = prev;
|
|
|
|
while (e != null) {
|
|
Entry<K,V> next = e.next;
|
|
if (h == e.hash && e.equals(entry)) {
|
|
modCount++;
|
|
size--;
|
|
if (prev == e)
|
|
tab[i] = next;
|
|
else
|
|
prev.next = next;
|
|
return true;
|
|
}
|
|
prev = e;
|
|
e = next;
|
|
}
|
|
|
|
return false;
|
|
}
|
|
|
|
/**
|
|
* Removes all of the mappings from this map.
|
|
* The map will be empty after this call returns.
|
|
*/
|
|
public void clear() {
|
|
// clear out ref queue. We don't need to expunge entries
|
|
// since table is getting cleared.
|
|
while (queue.poll() != null)
|
|
;
|
|
|
|
modCount++;
|
|
Arrays.fill(table, null);
|
|
size = 0;
|
|
|
|
// Allocation of array may have caused GC, which may have caused
|
|
// additional entries to go stale. Removing these entries from the
|
|
// reference queue will make them eligible for reclamation.
|
|
while (queue.poll() != null)
|
|
;
|
|
}
|
|
|
|
/**
|
|
* Returns {@code true} if this map maps one or more keys to the
|
|
* specified value.
|
|
*
|
|
* @param value value whose presence in this map is to be tested
|
|
* @return {@code true} if this map maps one or more keys to the
|
|
* specified value
|
|
*/
|
|
public boolean containsValue(Object value) {
|
|
if (value==null)
|
|
return containsNullValue();
|
|
|
|
Entry<K,V>[] tab = getTable();
|
|
for (int i = tab.length; i-- > 0;)
|
|
for (Entry<K,V> e = tab[i]; e != null; e = e.next)
|
|
if (value.equals(e.value))
|
|
return true;
|
|
return false;
|
|
}
|
|
|
|
/**
|
|
* Special-case code for containsValue with null argument
|
|
*/
|
|
private boolean containsNullValue() {
|
|
Entry<K,V>[] tab = getTable();
|
|
for (int i = tab.length; i-- > 0;)
|
|
for (Entry<K,V> e = tab[i]; e != null; e = e.next)
|
|
if (e.value==null)
|
|
return true;
|
|
return false;
|
|
}
|
|
|
|
/**
|
|
* The entries in this hash table extend WeakReference, using its main ref
|
|
* field as the key.
|
|
*/
|
|
private static class Entry<K,V> extends WeakReference<Object> implements Map.Entry<K,V> {
|
|
V value;
|
|
final int hash;
|
|
Entry<K,V> next;
|
|
|
|
/**
|
|
* Creates new entry.
|
|
*/
|
|
Entry(Object key, V value,
|
|
ReferenceQueue<Object> queue,
|
|
int hash, Entry<K,V> next) {
|
|
super(key, queue);
|
|
this.value = value;
|
|
this.hash = hash;
|
|
this.next = next;
|
|
}
|
|
|
|
@SuppressWarnings("unchecked")
|
|
public K getKey() {
|
|
return (K) WeakHashMap.unmaskNull(get());
|
|
}
|
|
|
|
public V getValue() {
|
|
return value;
|
|
}
|
|
|
|
public V setValue(V newValue) {
|
|
V oldValue = value;
|
|
value = newValue;
|
|
return oldValue;
|
|
}
|
|
|
|
public boolean equals(Object o) {
|
|
if (!(o instanceof Map.Entry<?, ?> e))
|
|
return false;
|
|
K k1 = getKey();
|
|
Object k2 = e.getKey();
|
|
if (k1 == k2 || (k1 != null && k1.equals(k2))) {
|
|
V v1 = getValue();
|
|
Object v2 = e.getValue();
|
|
if (v1 == v2 || (v1 != null && v1.equals(v2)))
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
public int hashCode() {
|
|
K k = getKey();
|
|
V v = getValue();
|
|
return Objects.hashCode(k) ^ Objects.hashCode(v);
|
|
}
|
|
|
|
public String toString() {
|
|
return getKey() + "=" + getValue();
|
|
}
|
|
}
|
|
|
|
private abstract class HashIterator<T> implements Iterator<T> {
|
|
private int index;
|
|
private Entry<K,V> entry;
|
|
private Entry<K,V> lastReturned;
|
|
private int expectedModCount = modCount;
|
|
|
|
/**
|
|
* Strong reference needed to avoid disappearance of key
|
|
* between hasNext and next
|
|
*/
|
|
private Object nextKey;
|
|
|
|
/**
|
|
* Strong reference needed to avoid disappearance of key
|
|
* between nextEntry() and any use of the entry
|
|
*/
|
|
private Object currentKey;
|
|
|
|
HashIterator() {
|
|
index = isEmpty() ? 0 : table.length;
|
|
}
|
|
|
|
public boolean hasNext() {
|
|
Entry<K,V>[] t = table;
|
|
|
|
while (nextKey == null) {
|
|
Entry<K,V> e = entry;
|
|
int i = index;
|
|
while (e == null && i > 0)
|
|
e = t[--i];
|
|
entry = e;
|
|
index = i;
|
|
if (e == null) {
|
|
currentKey = null;
|
|
return false;
|
|
}
|
|
nextKey = e.get(); // hold on to key in strong ref
|
|
if (nextKey == null)
|
|
entry = entry.next;
|
|
}
|
|
return true;
|
|
}
|
|
|
|
/** The common parts of next() across different types of iterators */
|
|
protected Entry<K,V> nextEntry() {
|
|
if (modCount != expectedModCount)
|
|
throw new ConcurrentModificationException();
|
|
if (nextKey == null && !hasNext())
|
|
throw new NoSuchElementException();
|
|
|
|
lastReturned = entry;
|
|
entry = entry.next;
|
|
currentKey = nextKey;
|
|
nextKey = null;
|
|
return lastReturned;
|
|
}
|
|
|
|
public void remove() {
|
|
if (lastReturned == null)
|
|
throw new IllegalStateException();
|
|
if (modCount != expectedModCount)
|
|
throw new ConcurrentModificationException();
|
|
|
|
WeakHashMap.this.remove(currentKey);
|
|
expectedModCount = modCount;
|
|
lastReturned = null;
|
|
currentKey = null;
|
|
}
|
|
|
|
}
|
|
|
|
private class ValueIterator extends HashIterator<V> {
|
|
public V next() {
|
|
return nextEntry().value;
|
|
}
|
|
}
|
|
|
|
private class KeyIterator extends HashIterator<K> {
|
|
public K next() {
|
|
return nextEntry().getKey();
|
|
}
|
|
}
|
|
|
|
private class EntryIterator extends HashIterator<Map.Entry<K,V>> {
|
|
public Map.Entry<K,V> next() {
|
|
return nextEntry();
|
|
}
|
|
}
|
|
|
|
// Views
|
|
|
|
private transient Set<Map.Entry<K,V>> entrySet;
|
|
|
|
/**
|
|
* Returns a {@link Set} view of the keys contained in this map.
|
|
* The set is backed by the map, so changes to the map are
|
|
* reflected in the set, and vice-versa. If the map is modified
|
|
* while an iteration over the set is in progress (except through
|
|
* the iterator's own {@code remove} operation), the results of
|
|
* the iteration are undefined. The set supports element removal,
|
|
* which removes the corresponding mapping from the map, via the
|
|
* {@code Iterator.remove}, {@code Set.remove},
|
|
* {@code removeAll}, {@code retainAll}, and {@code clear}
|
|
* operations. It does not support the {@code add} or {@code addAll}
|
|
* operations.
|
|
*/
|
|
public Set<K> keySet() {
|
|
Set<K> ks = keySet;
|
|
if (ks == null) {
|
|
ks = new KeySet();
|
|
keySet = ks;
|
|
}
|
|
return ks;
|
|
}
|
|
|
|
private class KeySet extends AbstractSet<K> {
|
|
public Iterator<K> iterator() {
|
|
return new KeyIterator();
|
|
}
|
|
|
|
public int size() {
|
|
return WeakHashMap.this.size();
|
|
}
|
|
|
|
public boolean contains(Object o) {
|
|
return containsKey(o);
|
|
}
|
|
|
|
public boolean remove(Object o) {
|
|
if (containsKey(o)) {
|
|
WeakHashMap.this.remove(o);
|
|
return true;
|
|
}
|
|
else
|
|
return false;
|
|
}
|
|
|
|
public void clear() {
|
|
WeakHashMap.this.clear();
|
|
}
|
|
|
|
public Spliterator<K> spliterator() {
|
|
return new KeySpliterator<>(WeakHashMap.this, 0, -1, 0, 0);
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Returns a {@link Collection} view of the values contained in this map.
|
|
* The collection is backed by the map, so changes to the map are
|
|
* reflected in the collection, and vice-versa. If the map is
|
|
* modified while an iteration over the collection is in progress
|
|
* (except through the iterator's own {@code remove} operation),
|
|
* the results of the iteration are undefined. The collection
|
|
* supports element removal, which removes the corresponding
|
|
* mapping from the map, via the {@code Iterator.remove},
|
|
* {@code Collection.remove}, {@code removeAll},
|
|
* {@code retainAll} and {@code clear} operations. It does not
|
|
* support the {@code add} or {@code addAll} operations.
|
|
*/
|
|
public Collection<V> values() {
|
|
Collection<V> vs = values;
|
|
if (vs == null) {
|
|
vs = new Values();
|
|
values = vs;
|
|
}
|
|
return vs;
|
|
}
|
|
|
|
private class Values extends AbstractCollection<V> {
|
|
public Iterator<V> iterator() {
|
|
return new ValueIterator();
|
|
}
|
|
|
|
public int size() {
|
|
return WeakHashMap.this.size();
|
|
}
|
|
|
|
public boolean contains(Object o) {
|
|
return containsValue(o);
|
|
}
|
|
|
|
public void clear() {
|
|
WeakHashMap.this.clear();
|
|
}
|
|
|
|
public Spliterator<V> spliterator() {
|
|
return new ValueSpliterator<>(WeakHashMap.this, 0, -1, 0, 0);
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Returns a {@link Set} view of the mappings contained in this map.
|
|
* The set is backed by the map, so changes to the map are
|
|
* reflected in the set, and vice-versa. If the map is modified
|
|
* while an iteration over the set is in progress (except through
|
|
* the iterator's own {@code remove} operation, or through the
|
|
* {@code setValue} operation on a map entry returned by the
|
|
* iterator) the results of the iteration are undefined. The set
|
|
* supports element removal, which removes the corresponding
|
|
* mapping from the map, via the {@code Iterator.remove},
|
|
* {@code Set.remove}, {@code removeAll}, {@code retainAll} and
|
|
* {@code clear} operations. It does not support the
|
|
* {@code add} or {@code addAll} operations.
|
|
*/
|
|
public Set<Map.Entry<K,V>> entrySet() {
|
|
Set<Map.Entry<K,V>> es = entrySet;
|
|
return es != null ? es : (entrySet = new EntrySet());
|
|
}
|
|
|
|
private class EntrySet extends AbstractSet<Map.Entry<K,V>> {
|
|
public Iterator<Map.Entry<K,V>> iterator() {
|
|
return new EntryIterator();
|
|
}
|
|
|
|
public boolean contains(Object o) {
|
|
return o instanceof Map.Entry<?, ?> e
|
|
&& getEntry(e.getKey()) != null
|
|
&& getEntry(e.getKey()).equals(e);
|
|
}
|
|
|
|
public boolean remove(Object o) {
|
|
return removeMapping(o);
|
|
}
|
|
|
|
public int size() {
|
|
return WeakHashMap.this.size();
|
|
}
|
|
|
|
public void clear() {
|
|
WeakHashMap.this.clear();
|
|
}
|
|
|
|
private List<Map.Entry<K,V>> deepCopy() {
|
|
List<Map.Entry<K,V>> list = new ArrayList<>(size());
|
|
for (Map.Entry<K,V> e : this)
|
|
list.add(new AbstractMap.SimpleEntry<>(e));
|
|
return list;
|
|
}
|
|
|
|
public Object[] toArray() {
|
|
return deepCopy().toArray();
|
|
}
|
|
|
|
public <T> T[] toArray(T[] a) {
|
|
return deepCopy().toArray(a);
|
|
}
|
|
|
|
public Spliterator<Map.Entry<K,V>> spliterator() {
|
|
return new EntrySpliterator<>(WeakHashMap.this, 0, -1, 0, 0);
|
|
}
|
|
}
|
|
|
|
@SuppressWarnings("unchecked")
|
|
@Override
|
|
public void forEach(BiConsumer<? super K, ? super V> action) {
|
|
Objects.requireNonNull(action);
|
|
int expectedModCount = modCount;
|
|
|
|
Entry<K, V>[] tab = getTable();
|
|
for (Entry<K, V> entry : tab) {
|
|
while (entry != null) {
|
|
Object key = entry.get();
|
|
if (key != null) {
|
|
action.accept((K)WeakHashMap.unmaskNull(key), entry.value);
|
|
}
|
|
entry = entry.next;
|
|
|
|
if (expectedModCount != modCount) {
|
|
throw new ConcurrentModificationException();
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
@SuppressWarnings("unchecked")
|
|
@Override
|
|
public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) {
|
|
Objects.requireNonNull(function);
|
|
int expectedModCount = modCount;
|
|
|
|
Entry<K, V>[] tab = getTable();;
|
|
for (Entry<K, V> entry : tab) {
|
|
while (entry != null) {
|
|
Object key = entry.get();
|
|
if (key != null) {
|
|
entry.value = function.apply((K)WeakHashMap.unmaskNull(key), entry.value);
|
|
}
|
|
entry = entry.next;
|
|
|
|
if (expectedModCount != modCount) {
|
|
throw new ConcurrentModificationException();
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Similar form as other hash Spliterators, but skips dead
|
|
* elements.
|
|
*/
|
|
static class WeakHashMapSpliterator<K,V> {
|
|
final WeakHashMap<K,V> map;
|
|
WeakHashMap.Entry<K,V> current; // current node
|
|
int index; // current index, modified on advance/split
|
|
int fence; // -1 until first use; then one past last index
|
|
int est; // size estimate
|
|
int expectedModCount; // for comodification checks
|
|
|
|
WeakHashMapSpliterator(WeakHashMap<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) {
|
|
WeakHashMap<K,V> m = map;
|
|
est = m.size();
|
|
expectedModCount = m.modCount;
|
|
hi = fence = m.table.length;
|
|
}
|
|
return hi;
|
|
}
|
|
|
|
public final long estimateSize() {
|
|
getFence(); // force init
|
|
return (long) est;
|
|
}
|
|
}
|
|
|
|
static final class KeySpliterator<K,V>
|
|
extends WeakHashMapSpliterator<K,V>
|
|
implements Spliterator<K> {
|
|
KeySpliterator(WeakHashMap<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) ? 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();
|
|
WeakHashMap<K,V> m = map;
|
|
WeakHashMap.Entry<K,V>[] tab = m.table;
|
|
if ((hi = fence) < 0) {
|
|
mc = expectedModCount = m.modCount;
|
|
hi = fence = tab.length;
|
|
}
|
|
else
|
|
mc = expectedModCount;
|
|
if (tab.length >= hi && (i = index) >= 0 &&
|
|
(i < (index = hi) || current != null)) {
|
|
WeakHashMap.Entry<K,V> p = current;
|
|
current = null; // exhaust
|
|
do {
|
|
if (p == null)
|
|
p = tab[i++];
|
|
else {
|
|
Object x = p.get();
|
|
p = p.next;
|
|
if (x != null) {
|
|
@SuppressWarnings("unchecked") K k =
|
|
(K) WeakHashMap.unmaskNull(x);
|
|
action.accept(k);
|
|
}
|
|
}
|
|
} 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();
|
|
WeakHashMap.Entry<K,V>[] tab = map.table;
|
|
if (tab.length >= (hi = getFence()) && index >= 0) {
|
|
while (current != null || index < hi) {
|
|
if (current == null)
|
|
current = tab[index++];
|
|
else {
|
|
Object x = current.get();
|
|
current = current.next;
|
|
if (x != null) {
|
|
@SuppressWarnings("unchecked") K k =
|
|
(K) WeakHashMap.unmaskNull(x);
|
|
action.accept(k);
|
|
if (map.modCount != expectedModCount)
|
|
throw new ConcurrentModificationException();
|
|
return true;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
return false;
|
|
}
|
|
|
|
public int characteristics() {
|
|
return Spliterator.DISTINCT;
|
|
}
|
|
}
|
|
|
|
static final class ValueSpliterator<K,V>
|
|
extends WeakHashMapSpliterator<K,V>
|
|
implements Spliterator<V> {
|
|
ValueSpliterator(WeakHashMap<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) ? 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();
|
|
WeakHashMap<K,V> m = map;
|
|
WeakHashMap.Entry<K,V>[] tab = m.table;
|
|
if ((hi = fence) < 0) {
|
|
mc = expectedModCount = m.modCount;
|
|
hi = fence = tab.length;
|
|
}
|
|
else
|
|
mc = expectedModCount;
|
|
if (tab.length >= hi && (i = index) >= 0 &&
|
|
(i < (index = hi) || current != null)) {
|
|
WeakHashMap.Entry<K,V> p = current;
|
|
current = null; // exhaust
|
|
do {
|
|
if (p == null)
|
|
p = tab[i++];
|
|
else {
|
|
Object x = p.get();
|
|
V v = p.value;
|
|
p = p.next;
|
|
if (x != null)
|
|
action.accept(v);
|
|
}
|
|
} 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();
|
|
WeakHashMap.Entry<K,V>[] tab = map.table;
|
|
if (tab.length >= (hi = getFence()) && index >= 0) {
|
|
while (current != null || index < hi) {
|
|
if (current == null)
|
|
current = tab[index++];
|
|
else {
|
|
Object x = current.get();
|
|
V v = current.value;
|
|
current = current.next;
|
|
if (x != null) {
|
|
action.accept(v);
|
|
if (map.modCount != expectedModCount)
|
|
throw new ConcurrentModificationException();
|
|
return true;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
return false;
|
|
}
|
|
|
|
public int characteristics() {
|
|
return 0;
|
|
}
|
|
}
|
|
|
|
static final class EntrySpliterator<K,V>
|
|
extends WeakHashMapSpliterator<K,V>
|
|
implements Spliterator<Map.Entry<K,V>> {
|
|
EntrySpliterator(WeakHashMap<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) ? 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();
|
|
WeakHashMap<K,V> m = map;
|
|
WeakHashMap.Entry<K,V>[] tab = m.table;
|
|
if ((hi = fence) < 0) {
|
|
mc = expectedModCount = m.modCount;
|
|
hi = fence = tab.length;
|
|
}
|
|
else
|
|
mc = expectedModCount;
|
|
if (tab.length >= hi && (i = index) >= 0 &&
|
|
(i < (index = hi) || current != null)) {
|
|
WeakHashMap.Entry<K,V> p = current;
|
|
current = null; // exhaust
|
|
do {
|
|
if (p == null)
|
|
p = tab[i++];
|
|
else {
|
|
Object x = p.get();
|
|
V v = p.value;
|
|
p = p.next;
|
|
if (x != null) {
|
|
@SuppressWarnings("unchecked") K k =
|
|
(K) WeakHashMap.unmaskNull(x);
|
|
action.accept
|
|
(new AbstractMap.SimpleImmutableEntry<>(k, v));
|
|
}
|
|
}
|
|
} 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();
|
|
WeakHashMap.Entry<K,V>[] tab = map.table;
|
|
if (tab.length >= (hi = getFence()) && index >= 0) {
|
|
while (current != null || index < hi) {
|
|
if (current == null)
|
|
current = tab[index++];
|
|
else {
|
|
Object x = current.get();
|
|
V v = current.value;
|
|
current = current.next;
|
|
if (x != null) {
|
|
@SuppressWarnings("unchecked") K k =
|
|
(K) WeakHashMap.unmaskNull(x);
|
|
action.accept
|
|
(new AbstractMap.SimpleImmutableEntry<>(k, v));
|
|
if (map.modCount != expectedModCount)
|
|
throw new ConcurrentModificationException();
|
|
return true;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
return false;
|
|
}
|
|
|
|
public int characteristics() {
|
|
return Spliterator.DISTINCT;
|
|
}
|
|
}
|
|
|
|
}
|