| /* |
| * Copyright (c) 1997, 2006, 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; |
| |
| /** |
| * This class provides a skeletal implementation of the <tt>Set</tt> |
| * interface to minimize the effort required to implement this |
| * interface. <p> |
| * |
| * The process of implementing a set by extending this class is identical |
| * to that of implementing a Collection by extending AbstractCollection, |
| * except that all of the methods and constructors in subclasses of this |
| * class must obey the additional constraints imposed by the <tt>Set</tt> |
| * interface (for instance, the add method must not permit addition of |
| * multiple instances of an object to a set).<p> |
| * |
| * Note that this class does not override any of the implementations from |
| * the <tt>AbstractCollection</tt> class. It merely adds implementations |
| * for <tt>equals</tt> and <tt>hashCode</tt>.<p> |
| * |
| * This class is a member of the |
| * <a href="{@docRoot}/../technotes/guides/collections/index.html"> |
| * Java Collections Framework</a>. |
| * |
| * @param <E> the type of elements maintained by this set |
| * |
| * @author Josh Bloch |
| * @author Neal Gafter |
| * @see Collection |
| * @see AbstractCollection |
| * @see Set |
| * @since 1.2 |
| */ |
| |
| public abstract class AbstractSet<E> extends AbstractCollection<E> implements Set<E> { |
| /** |
| * Sole constructor. (For invocation by subclass constructors, typically |
| * implicit.) |
| */ |
| protected AbstractSet() { |
| } |
| |
| // Comparison and hashing |
| |
| /** |
| * Compares the specified object with this set for equality. Returns |
| * <tt>true</tt> if the given object is also a set, the two sets have |
| * the same size, and every member of the given set is contained in |
| * this set. This ensures that the <tt>equals</tt> method works |
| * properly across different implementations of the <tt>Set</tt> |
| * interface.<p> |
| * |
| * This implementation first checks if the specified object is this |
| * set; if so it returns <tt>true</tt>. Then, it checks if the |
| * specified object is a set whose size is identical to the size of |
| * this set; if not, it returns false. If so, it returns |
| * <tt>containsAll((Collection) o)</tt>. |
| * |
| * @param o object to be compared for equality with this set |
| * @return <tt>true</tt> if the specified object is equal to this set |
| */ |
| public boolean equals(Object o) { |
| if (o == this) |
| return true; |
| |
| if (!(o instanceof Set)) |
| return false; |
| Collection c = (Collection) o; |
| if (c.size() != size()) |
| return false; |
| try { |
| return containsAll(c); |
| } catch (ClassCastException unused) { |
| return false; |
| } catch (NullPointerException unused) { |
| return false; |
| } |
| } |
| |
| /** |
| * Returns the hash code value for this set. The hash code of a set is |
| * defined to be the sum of the hash codes of the elements in the set, |
| * where the hash code of a <tt>null</tt> element is defined to be zero. |
| * This ensures that <tt>s1.equals(s2)</tt> implies that |
| * <tt>s1.hashCode()==s2.hashCode()</tt> for any two sets <tt>s1</tt> |
| * and <tt>s2</tt>, as required by the general contract of |
| * {@link Object#hashCode}. |
| * |
| * <p>This implementation iterates over the set, calling the |
| * <tt>hashCode</tt> method on each element in the set, and adding up |
| * the results. |
| * |
| * @return the hash code value for this set |
| * @see Object#equals(Object) |
| * @see Set#equals(Object) |
| */ |
| public int hashCode() { |
| int h = 0; |
| Iterator<E> i = iterator(); |
| while (i.hasNext()) { |
| E obj = i.next(); |
| if (obj != null) |
| h += obj.hashCode(); |
| } |
| return h; |
| } |
| |
| /** |
| * Removes from this set all of its elements that are contained in the |
| * specified collection (optional operation). If the specified |
| * collection is also a set, this operation effectively modifies this |
| * set so that its value is the <i>asymmetric set difference</i> of |
| * the two sets. |
| * |
| * <p>This implementation determines which is the smaller of this set |
| * and the specified collection, by invoking the <tt>size</tt> |
| * method on each. If this set has fewer elements, then the |
| * implementation iterates over this set, checking each element |
| * returned by the iterator in turn to see if it is contained in |
| * the specified collection. If it is so contained, it is removed |
| * from this set with the iterator's <tt>remove</tt> method. If |
| * the specified collection has fewer elements, then the |
| * implementation iterates over the specified collection, removing |
| * from this set each element returned by the iterator, using this |
| * set's <tt>remove</tt> method. |
| * |
| * <p>Note that this implementation will throw an |
| * <tt>UnsupportedOperationException</tt> if the iterator returned by the |
| * <tt>iterator</tt> method does not implement the <tt>remove</tt> method. |
| * |
| * @param c collection containing elements to be removed from this set |
| * @return <tt>true</tt> if this set changed as a result of the call |
| * @throws UnsupportedOperationException if the <tt>removeAll</tt> operation |
| * is not supported by this set |
| * @throws ClassCastException if the class of an element of this set |
| * is incompatible with the specified collection |
| * (<a href="Collection.html#optional-restrictions">optional</a>) |
| * @throws NullPointerException if this set contains a null element and the |
| * specified collection does not permit null elements |
| * (<a href="Collection.html#optional-restrictions">optional</a>), |
| * or if the specified collection is null |
| * @see #remove(Object) |
| * @see #contains(Object) |
| */ |
| public boolean removeAll(Collection<?> c) { |
| boolean modified = false; |
| |
| if (size() > c.size()) { |
| for (Iterator<?> i = c.iterator(); i.hasNext(); ) |
| modified |= remove(i.next()); |
| } else { |
| for (Iterator<?> i = iterator(); i.hasNext(); ) { |
| if (c.contains(i.next())) { |
| i.remove(); |
| modified = true; |
| } |
| } |
| } |
| return modified; |
| } |
| |
| } |
