| /* AbstractSet.java -- Abstract implementation of most of Set |
| Copyright (C) 1998, 2000, 2001, 2005 Free Software Foundation, Inc. |
| |
| This file is part of GNU Classpath. |
| |
| GNU Classpath is free software; you can redistribute it and/or modify |
| it under the terms of the GNU General Public License as published by |
| the Free Software Foundation; either version 2, or (at your option) |
| any later version. |
| |
| GNU Classpath 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 for more details. |
| |
| You should have received a copy of the GNU General Public License |
| along with GNU Classpath; see the file COPYING. If not, write to the |
| Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA |
| 02111-1307 USA. |
| |
| Linking this library statically or dynamically with other modules is |
| making a combined work based on this library. Thus, the terms and |
| conditions of the GNU General Public License cover the whole |
| combination. |
| |
| As a special exception, the copyright holders of this library give you |
| permission to link this library with independent modules to produce an |
| executable, regardless of the license terms of these independent |
| modules, and to copy and distribute the resulting executable under |
| terms of your choice, provided that you also meet, for each linked |
| independent module, the terms and conditions of the license of that |
| module. An independent module is a module which is not derived from |
| or based on this library. If you modify this library, you may extend |
| this exception to your version of the library, but you are not |
| obligated to do so. If you do not wish to do so, delete this |
| exception statement from your version. */ |
| |
| |
| package java.util; |
| |
| /** |
| * An abstract implementation of Set to make it easier to create your own |
| * implementations. In order to create a Set, subclass AbstractSet and |
| * implement the same methods that are required for AbstractCollection |
| * (although these methods must of course meet the requirements that Set puts |
| * on them - specifically, no element may be in the set more than once). This |
| * class simply provides implementations of equals() and hashCode() to fulfil |
| * the requirements placed on them by the Set interface. |
| * |
| * @author Original author unknown |
| * @author Eric Blake (ebb9@email.byu.edu) |
| * @see Collection |
| * @see AbstractCollection |
| * @see Set |
| * @see HashSet |
| * @see TreeSet |
| * @see LinkedHashSet |
| * @since 1.2 |
| * @status updated to 1.4 |
| */ |
| public abstract class AbstractSet extends AbstractCollection implements Set |
| { |
| /** |
| * The main constructor, for use by subclasses. |
| */ |
| protected AbstractSet() |
| { |
| } |
| |
| /** |
| * Tests whether the given object is equal to this Set. This implementation |
| * first checks whether this set <em>is</em> the given object, and returns |
| * true if so. Otherwise, if o is a Set and is the same size as this one, it |
| * returns the result of calling containsAll on the given Set. Otherwise, it |
| * returns false. |
| * |
| * @param o the Object to be tested for equality with this Set |
| * @return true if the given object is equal to this Set |
| */ |
| public boolean equals(Object o) |
| { |
| return (o == this || |
| (o instanceof Set && ((Set) o).size() == size() |
| && containsAll((Collection) o))); |
| } |
| |
| /** |
| * Returns a hash code for this Set. The hash code of a Set is the sum of the |
| * hash codes of all its elements, except that the hash code of null is |
| * defined to be zero. This implementation obtains an Iterator over the Set, |
| * and sums the results. |
| * |
| * @return a hash code for this Set |
| */ |
| public int hashCode() |
| { |
| Iterator itr = iterator(); |
| int hash = 0; |
| int pos = size(); |
| while (--pos >= 0) |
| hash += hashCode(itr.next()); |
| return hash; |
| } |
| |
| /** |
| * Removes from this set all elements in the given collection (optional |
| * operation). This implementation uses <code>size()</code> to determine |
| * the smaller collection. Then, if this set is smaller, it iterates |
| * over the set, calling Iterator.remove if the collection contains |
| * the element. If this set is larger, it iterates over the collection, |
| * calling Set.remove for all elements in the collection. Note that |
| * this operation will fail if a remove methods is not supported. |
| * |
| * @param c the collection of elements to remove |
| * @return true if the set was modified as a result |
| * @throws UnsupportedOperationException if remove is not supported |
| * @throws NullPointerException if the collection is null |
| * @see AbstractCollection#remove(Object) |
| * @see Collection#contains(Object) |
| * @see Iterator#remove() |
| */ |
| public boolean removeAll(Collection c) |
| { |
| int oldsize = size(); |
| int count = c.size(); |
| Iterator i; |
| if (oldsize < count) |
| { |
| for (i = iterator(), count = oldsize; count > 0; count--) |
| if (c.contains(i.next())) |
| i.remove(); |
| } |
| else |
| for (i = c.iterator(); count > 0; count--) |
| remove(i.next()); |
| return oldsize != size(); |
| } |
| |
| } |