ListSet.java Source code

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Here is the source code for ListSet.java

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import java.io.Serializable;
import java.util.AbstractSet;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;
import java.util.Set;

/**
 * A thin wrapper around a <code>List</code> transforming it into a modifiable
 * <code>Set</code>.
 * 
 * @version <tt>$Revision: 2800 $</tt>
 * @author <a href="mailto:jason@planet57.com">Jason Dillon</a>
 */
@SuppressWarnings("unchecked")
public class ListSet extends AbstractSet implements Set, Cloneable, Serializable {
    /** The serialVersionUID */
    private 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 RuntimeException("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();
        }
    }
}