/**
  * @param x to be included in the hash code generation.
  * @return this
  */
 @Nonnull
 public HashCodeGenerator append(@Nullable final Node x) {
   _checkClosed();
   m_nHC = HashCodeCalculator.append(m_nHC, x);
   return this;
 }
 /**
  * Atomic type hash code generation.
  *
  * @param x Array to add
  * @return this
  */
 @Nonnull
 public HashCodeGenerator append(final short x) {
   _checkClosed();
   m_nHC = HashCodeCalculator.append(m_nHC, x);
   return this;
 }