Bug 133375 [Viewers] Need access to the element comparer of a tree selection
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/CustomHashtable.java
this(DEFAULT_CAPACITY, comparer);
    }
    /**
     * Constructs a new hash table with the given capacity and the given
     * element comparer.
     * 
     * @param capacity the maximum number of elements that can be added without
     *   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(int capacity, IElementComparer comparer) {
        if (capacity >= 0) {
            elementCount = 0;
            elementData = new HashMapEntry[capacity == 0 ? 1 : capacity];
            firstSlot = elementData.length;
            loadFactor = 0.75f;
            computeMaxSize();
        } else {
			throw new IllegalArgumentException();
		}
        this.comparer = comparer;
    }
    /**
     * Constructs a new hash table with enough capacity to hold all keys in the
     * given hash table, then adds all key/value pairs in the given hash table
     * to the new one, using the given element comparer.
     * 
     * @param capacity the maximum number of elements that can be added without