Small sets whose elements are known to be unique by construction : Set « Collections Data Structure « Java

Small sets whose elements are known to be unique by construction

 * JGraphT : a free Java graph-theory library
 * Project Info:
 * Project Creator:  Barak Naveh (
 * (C) Copyright 2003-2007, by Barak Naveh and Contributors.
 * This library is free software; you can redistribute it and/or modify it
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 * (at your option) any later version.
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 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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 * License for more details.
 * You should have received a copy of the GNU Lesser General Public License
 * along with this library; if not, write to the Free Software Foundation,
 * Inc.,
 * 59 Temple Place, Suite 330, Boston, MA 02111-1307, USA.
/* -----------------
 * -----------------
 * (C) Copyright 2006-2007, by John V. Sichi and Contributors.
 * Original Author:  John V. Sichi
 * Contributor(s):   -
 * $Id: 568 2007-09-30 00:12:18Z perfecthash $
 * Changes
 * -------
 * 07-May-2006 : Initial version (JVS);

import java.util.*;

 * Helper for efficiently representing small sets whose elements are known to be
 * unique by construction, implying we don't need to enforce the uniqueness
 * property in the data structure itself. Use with caution.
 * <p>Note that for equals/hashCode, the class implements the Set behavior
 * (unordered), not the list behavior (ordered); the fact that it subclasses
 * ArrayList should be considered an implementation detail.
 * @author John V. Sichi
public class ArrayUnenforcedSet<E>
    extends ArrayList<E>
    implements Set<E>
    //~ Static fields/initializers ---------------------------------------------

    private static final long serialVersionUID = -7413250161201811238L;

    //~ Constructors -----------------------------------------------------------

    public ArrayUnenforcedSet()

    public ArrayUnenforcedSet(Collection<? extends E> c)

    public ArrayUnenforcedSet(int n)

    //~ Methods ----------------------------------------------------------------

    public boolean equals(Object o)
        return new SetForEquality().equals(o);

    public int hashCode()
        return new SetForEquality().hashCode();

    //~ Inner Classes ----------------------------------------------------------

     * Multiple inheritance helper.
    private class SetForEquality
        extends AbstractSet<E>
        public Iterator<E> iterator()
            return ArrayUnenforcedSet.this.iterator();

        public int size()
            return ArrayUnenforcedSet.this.size();

// End


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