https://javabook.mccue.dev/class_extension/abstract_classes
id probably add a sentence or example to point out that the FiveAndSeven list now got hands on a lot of methods for free coming from AbstractList.
like, u sorta mentioned it in the comment but i think using two or three more methods in the main example down there (or adding an extra sentence) to point this out more would be useful
originally suggested in the TJ discord by zabuzard.