code: protected static Object clear (
          EqualityComparator eqc, Object[] list, Object element)
      {
          int dex = indexOf(eqc, list, element);
          if (dex == -1) {
              return null;
          }
          Object elem = list[dex];
          list[dex] = null;
          return elem;
      }
docs: Helper function for {@link #clearRef}, etc.