This ability to implicitly treat instance methods as functions accepting their instance as a parameter is a powerful feature of Java’s lambda expressions and method references. It allows you to ...

The technique that a developer can use to apply method parameters as carriers for return data is to accept parameters that are mutable and to mutate the passed-in objects’ state.

At this point, the Scanner still returns a String, although the String contains only one character. To complete the use case, you must convert this one-character String into a single Java char with ...