The problem

My book on Java tries to introduce keyboard input as early as possible.

The technical preface says ‘the horrors of Java's keyboard input are introduced early (Chapter 4):

0008:       BufferedReader tKeyboard =
0009:             new BufferedReader(new InputStreamReader(System.in));
0010:       System.out.print("Type in your first number: ");
0011:       String tFirstString = tKeyboard.readLine();
0012:       double tFirst = Double.parseDouble(tFirstString);

Note the use of both instance methods and class methods and the need to use the wrapper classes of the primitive types.’