
dorkbox.collections.IdentitySet Maven / Gradle / Ivy
/*
* Copyright 2023 dorkbox, llc
*
* Licensed 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 dorkbox.collections;
import java.util.AbstractSet;
import java.util.Collection;
import java.util.ConcurrentModificationException;
import java.util.Iterator;
import java.util.Set;
public
class IdentitySet extends AbstractSet implements Set, Cloneable, java.io.Serializable {
private transient IdentityMap map;
// Dummy value to associate with an Object in the backing Map
private static final Object PRESENT = new Object();
/**
* Constructs a new, empty set; the backing HashMap instance has
* default initial capacity (16) and load factor (0.75).
*/
public
IdentitySet() {
map = new IdentityMap<>();
}
/**
* Constructs a new set containing the elements in the specified
* collection. The HashMap is created with default load factor
* (0.75) and an initial capacity sufficient to contain the elements in
* the specified collection.
*
* @param c the collection whose elements are to be placed into this set
*
* @throws NullPointerException if the specified collection is null
*/
public
IdentitySet(Collection extends E> c) {
map = new IdentityMap<>(Math.max((int) (c.size() / .75f) + 1, 16));
addAll(c);
}
/**
* Constructs a new, empty set; the backing HashMap instance has
* the specified initial capacity and default load factor (0.75).
*
* @param initialCapacity the initial capacity of the hash table
*
* @throws IllegalArgumentException if the initial capacity is less
* than zero
*/
public
IdentitySet(int initialCapacity) {
map = new IdentityMap<>(initialCapacity);
}
/**
* 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
*/
@Override
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)
*/
@Override
public
int size() {
return map.size();
}
/**
* Returns true if this set contains no elements.
*
* @return true if this set contains no elements
*/
@Override
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
*/
@Override
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
*/
@Override
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
*/
@Override
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.
*/
@Override
public
void clear() {
map.clear();
}
}
© 2015 - 2025 Weber Informatics LLC | Privacy Policy