@Override
  public int hashCode() {
    int hash = 1;
    if (fieldName != null) {
      hash = hash * 31 + fieldName.hashCode();
    }
    if (type != null) {
      hash = hash * 31 + type.hashCode();
    }

    return hash;
  }
Used by {@link PdxInstanceImpl#equals(Object)} to act as if it has a field whose value is
always the default.
geode-core/src/main/java/org/apache/geode/pdx/internal/PdxField.java