public Entry next() {
      while (next == null && index < table.length) {
        if (table[index] != null) {
          next = table[index];
        }
        index++;
      }

      Entry oldNext = next;
      if (oldNext != null) {
        next = oldNext.next;
      }
      return oldNext;
    }
Returns the next Entry to visit. Will return <code>null</code> after we have iterated through
all of the entries.
geode-core/src/main/java/org/apache/geode/internal/admin/ListenerIdMap.java