manipulator.java

interface DataManipulator {
  
  void clear();

  void from(DataHolder holder);

}

interface DisplayNameData extends DataManipulator {

  Optional<Message> getDisplayName();

  void setDisplayName(@Nullable Message displayName)

  void clearDisplayName();

}

interface DataHolder {
  
  <T> Optional<T extends DataManipulator> obtain(Class<T> manipulatorClass);

  boolean complies(Class<DataManipulator> manipulatorClass);

  void accept(DataManipulator manipulator);

}

// Get an instance to a fresh DisplayNameData
DisplayNameData data = DataManipulators.obtain(DisplayNameData.class);

// or, if we want a data manipulator with fields already set to an item stack's data
DisplayNameData data = myItemStack.obtain(DisplayNameData.class);

data.setDisplayName(Messages.of("new name"));

myItemStack.accept(data);
myOtherItemStack.accept(data);

data.setDisplayName(Messages.of("other new name"));

myItemStack.accept(data);