public void addInstanceField(EncodedField field){
  if (field == null) {
    throw new NullPointerException("field == null");
  }
  instanceFields.add(field);
}

public void addInstanceField ( EncodedField field ) { if ( field == null ) { throw new NullPointerException ( "field == null" ) ; } instanceFields . add ( field ) ; }
adds an instance field .
