Java Recipes : Sorting object

Easy it`s sorting Strings or Integers or Double or Chars (I know there is not often sytuation it happens).
When We have object must think and choose field to sort ( with hierarchy of values).
In java I find to implementation this problem:
1) all objects
2) choosen one field
How use with what`s problem I don`t know.

GITHUB LINK: https://github.com/mikoxp/javaRecipes/tree/master/sort_object/src