* @param obj object that will be wrapped
     * @param soft true if a SoftReference should be created; otherwise Soft
     * @return a Reference or null if obj is null.
     */
    static Reference createReference(Object obj, boolean soft) {
  Reference ref = null;
  if (obj != null) {
      if (soft) {
    ref = new SoftReference(obj);
      } else {
    ref = new WeakReference(obj);