/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF 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 java.util;
/**
* An AbstractSet is an abstract implementation of the Set interface. This
* implementation does not support adding. A subclass must implement the
* abstract methods iterator() and size().
*
* @since 1.2
*/
public abstract class AbstractSet<E> extends AbstractCollection<E> implements
Set<E> {
/**
* Constructs a new instance of this AbstractSet.
*/
protected AbstractSet() {
}
/**
* Compares the specified object to this Set and returns true if they are
* equal. The object must be an instance of Set and contain the same
* objects.
*
* @param object
* the object to compare with this set.
* @return {@code true} if the specified object is equal to this set,
* {@code false} otherwise
* @see #hashCode
*/
@Override
public boolean equals(Object object) {
if (this == object) {
return true;
}
if (object instanceof Set) {
Set<?> s = (Set<?>) object;
try {
return size() == s.size() && containsAll(s);
} catch (NullPointerException ignored) {
return false;
} catch (ClassCastException ignored) {
return false;
}
}
return false;
}
/**
* Returns the hash code for this set. Two set which are equal must return
* the same value. This implementation calculates the hash code by adding
* each element's hash code.
*
* @return the hash code of this set.
* @see #equals
*/
@Override
public int hashCode() {
int result = 0;
Iterator<?> it = iterator();
while (it.hasNext()) {
Object next = it.next();
result += next == null ? 0 : next.hashCode();
}
return result;
}
/**
* Removes all occurrences in this collection which are contained in the
* specified collection.
*
* @param collection
* the collection of objects to remove.
* @return {@code true} if this collection was modified, {@code false}
* otherwise.
* @throws UnsupportedOperationException
* if removing from this collection is not supported.
*/
@Override
public boolean removeAll(Collection<?> collection) {
boolean result = false;
if (size() <= collection.size()) {
Iterator<?> it = iterator();
while (it.hasNext()) {
if (collection.contains(it.next())) {
it.remove();
result = true;
}
}
} else {
Iterator<?> it = collection.iterator();
while (it.hasNext()) {
result = remove(it.next()) || result;
}
}
return result;
}
}