Bug 133375 [Viewers] Need access to the element comparer of a tree selection
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/CustomHashtable.java
private static final EmptyEnumerator emptyEnumerator = new EmptyEnumerator();
    /**
     * The default capacity used when not specified in the constructor.
     */
    public static final int DEFAULT_CAPACITY = 13;
    /**
     * Constructs a new Hashtable using the default capacity
     * and load factor.
     */
    public CustomHashtable() {
        this(13);
    }
    /**
     * Constructs a new Hashtable using the specified capacity
     * and the default load factor.
     *
     * @param capacity the initial capacity
     */
    public CustomHashtable(int capacity) {
        this(capacity, null);
    }
    /**
     * Constructs a new hash table with the default capacity and the given
     * element comparer.
     *
     * @param comparer the element comparer to use to compare keys and obtain
     *   hash codes for keys, or <code>null</code>  to use the normal 
     *   <code>equals</code> and <code>hashCode</code> methods
     */
    public CustomHashtable(IElementComparer comparer) {