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/*
* Licensed to Elastic Search and Shay Banon under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. Elastic Search licenses this
* file to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
package org.elasticsearch.common.collect;
import java.util.*;
/**
* @author kimchy (Shay Banon)
*/
public class IdentityHashSet
extends AbstractSet
implements Set, Cloneable, java.io.Serializable {
static final long serialVersionUID = -5024744406713321677L;
private transient IdentityHashMap map;
// Dummy value to associate with an Object in the backing Map
private static final Object PRESENT = new Object();
public IdentityHashSet() {
map = new IdentityHashMap();
}
public IdentityHashSet(Collection c) {
map = new IdentityHashMap(Math.max((int) (c.size() / .75f) + 1, 16));
addAll(c);
}
public IdentityHashSet(int expectedSize) {
map = new IdentityHashMap(expectedSize);
}
/**
* Returns an iterator over the elements in this set. The elements
* are returned in no particular order.
*
* @return an Iterator over the elements in this set
* @see ConcurrentModificationException
*/
public Iterator iterator() {
return map.keySet().iterator();
}
/**
* Returns the number of elements in this set (its cardinality).
*
* @return the number of elements in this set (its cardinality)
*/
public int size() {
return map.size();
}
/**
* Returns true if this set contains no elements.
*
* @return true if this set contains no elements
*/
public boolean isEmpty() {
return map.isEmpty();
}
/**
* Returns true if this set contains the specified element.
* More formally, returns true if and only if this set
* contains an element e such that
* (o==null ? e==null : o.equals(e)).
*
* @param o element whose presence in this set is to be tested
* @return true if this set contains the specified element
*/
public boolean contains(Object o) {
return map.containsKey(o);
}
/**
* Adds the specified element to this set if it is not already present.
* More formally, adds the specified element e to this set if
* this set contains no element e2 such that
* (e==null ? e2==null : e.equals(e2)).
* If this set already contains the element, the call leaves the set
* unchanged and returns false.
*
* @param e element to be added to this set
* @return true if this set did not already contain the specified
* element
*/
public boolean add(E e) {
return map.put(e, PRESENT) == null;
}
/**
* Removes the specified element from this set if it is present.
* More formally, removes an element e such that
* (o==null ? e==null : o.equals(e)),
* if this set contains such an element. Returns true if
* this set contained the element (or equivalently, if this set
* changed as a result of the call). (This set will not contain the
* element once the call returns.)
*
* @param o object to be removed from this set, if present
* @return true if the set contained the specified element
*/
public boolean remove(Object o) {
return map.remove(o) == PRESENT;
}
/**
* Removes all of the elements from this set.
* The set will be empty after this call returns.
*/
public void clear() {
map.clear();
}
/**
* Returns a shallow copy of this HashSet instance: the elements
* themselves are not cloned.
*
* @return a shallow copy of this set
*/
public Object clone() {
try {
IdentityHashSet newSet = (IdentityHashSet) super.clone();
newSet.map = (IdentityHashMap) map.clone();
return newSet;
} catch (CloneNotSupportedException e) {
throw new InternalError();
}
}
/**
* Index the state of this HashSet instance to a stream (that is,
* serialize it).
*
* @serialData The capacity of the backing HashMap instance
* (int), and its load factor (float) are emitted, followed by
* the size of the set (the number of elements it contains)
* (int), followed by all of its elements (each an Object) in
* no particular order.
*/
private void writeObject(java.io.ObjectOutputStream s)
throws java.io.IOException {
// Write out any hidden serialization magic
s.defaultWriteObject();
// Write out size
s.writeInt(map.size());
// Write out all elements in the proper order.
for (Iterator i = map.keySet().iterator(); i.hasNext();)
s.writeObject(i.next());
}
/**
* Reconstitute the HashSet instance from a stream (that is,
* deserialize it).
*/
private void readObject(java.io.ObjectInputStream s)
throws java.io.IOException, ClassNotFoundException {
// Read in any hidden serialization magic
s.defaultReadObject();
// Read in size
int size = s.readInt();
map = new IdentityHashMap(size);
// Read in all elements in the proper order.
for (int i = 0; i < size; i++) {
E e = (E) s.readObject();
map.put(e, PRESENT);
}
}
}