StringBuilder, regular expressions, enums and iterators
The tools that round off part 10. The traditional for loop once more, for counting down, taking steps and working with indexes; StringBuilder, for building a text piece by piece; regular expressions, which check the form of a string with matches, alternation, groups, quantifiers and character classes; enums, types with a fixed set of values, with fields, a constructor and methods of their own; and iterators, which can remove elements while going through a collection. Last, a look back at the whole of part 10. MOOC sections 10.3 and 10.4.