Bug 133375 [Viewers] Need access to the element comparer of a tree selection
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/CustomHashtable.java
*   rehashing
     * @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(CustomHashtable table, IElementComparer comparer) {
        this(table.size() * 2, comparer);
        for (int i = table.elementData.length; --i >= 0;) {
            HashMapEntry entry = table.elementData[i];
            while (entry != null) {
                put(entry.key, entry.value);
                entry = entry.next;
            }
        }
    }
    private void computeMaxSize() {
        threshold = (int) (elementData.length * loadFactor);
    }
    /**
     * Answers if this Hashtable contains the specified object as a key
     * of one of the key/value pairs.
     *
     * @param		key	the object to look for as a key in this Hashtable
     * @return		true if object is a key in this Hashtable, false otherwise
     */
    public boolean containsKey(Object key) {
        return getEntry(key) != null;
    }
    /**
     * Answers an Enumeration on the values of this Hashtable. The