ListSet.java |
/*************************************** * * * JBoss: The OpenSource J2EE WebOS * * * * Distributable under LGPL license. * * See terms of license at gnu.org. * * * ***************************************/ package org.jboss.util.collection; import java.util.List; import java.util.ArrayList; import java.util.Set; import java.util.AbstractSet; import java.util.Iterator; import java.util.Collection; import java.io.Serializable; import org.jboss.util.NullArgumentException; /** * A thin wrapper around a <code>List</code> transforming it into a * modifiable <code>Set</code>. * * @version <tt>$Revision: 1.5.6.1 $</tt> * @author <a href="mailto:jason@planet57.com">Jason Dillon</a> */ public class ListSet extends AbstractSet implements Set, Cloneable, Serializable { static final long serialVersionUID = 7333619218072079496L; /** The <tt>List</tt> which will be used for element storage. */ protected final List list; /** * Construct a <tt>ListSet</tt>. * * @param list The <tt>List</tt> which will be used for element storage. * * @throws IllegalArgumentException List is <tt>null</tt> or contains * duplicate entries. */ public ListSet(final List list) { if (list == null) throw new NullArgumentException("list"); // make sure there are no duplicates int size = list.size(); for (int i=0; i<size; i++) { Object obj = list.get(i); if (list.indexOf(obj) != list.lastIndexOf(obj)) { throw new IllegalArgumentException ("list contains duplicate entries"); } } this.list = list; } /** * Construct a <tt>ListSet</tt> using an <tt>ArrayList</tt> for backing. */ public ListSet() { this(new ArrayList()); } /** * Construct a <tt>ListSet</tt> using an <tt>ArrayList</tt> for backing * and populated with the given elements. * * @param elements The elements for the list. */ public ListSet(final Collection elements) { this(new ArrayList(elements)); } public List getList() { return list; } /** * Return the size of the set. * * @return The size of the set. */ public int size() { return list.size(); } /** * Return an iteration over the elements in the set. * * @return An iteration over the elements in the set. */ public Iterator iterator() { return list.iterator(); } /** * Add an element to the set. * * @param obj Element to add to the set. * @return True if the element was added. */ public boolean add(final Object obj) { boolean added = false; if (!list.contains(obj)) { added = list.add(obj); } return added; } /** * Returns <tt>true</tt> if this set contains no elements. * * @return <tt>true</tt> if this set contains no elements. */ public boolean isEmpty() { return list.isEmpty(); } /** * Returns <tt>true</tt> if this set contains the specified element. * * @param obj Element whose presence in this set is to be tested. * @return <tt>true</tt> if this set contains the specified element. */ public boolean contains(final Object obj) { return list.contains(obj); } /** * Removes the given element from this set if it is present. * * @param obj Object to be removed from this set, if present. * @return <tt>true</tt> if the set contained the specified element. */ public boolean remove(final Object obj) { return list.remove(obj); } /** * Removes all of the elements from this set. */ public void clear() { list.clear(); } /** * Returns a shallow copy of this <tt>ListSet</tt> instance. * * @return A shallow copy of this set. */ public Object clone() { try { return super.clone(); } catch (CloneNotSupportedException e) { throw new InternalError(); } } }
ListSet.java |