More-sophisticated behavior - Objects First with Java: A Practical Introduction Using BlueJ - page 160

program). We make sure that it is initially false . (Remember that the exclamation mark is a
not operator!)

The main part of the loop—the part that is done repeatedly while we wish to continue—consists
of three statements if we strip it of the check for the exit condition:

String input = reader.getInput();
...
String response = responder.generateResponse();
System.out.println(response);

Thus, the loop repeatedly
■ reads some user input,
■ asks the responder to generate a response, and

■ prints out that response.

(You may have noticed that the response does not depend on the input at all! This is certainly
something we shall have to improve later.)

The last part to examine is the check of the exit condition. The intention is that the program
should end once a user types the word 'bye'. The relevant section of source code we find in the
class reads

String input = reader.getInput();

if(input.startsWith("bye")) {
finished = true;
}

If you understand these pieces in isolation, then it is a good idea to look again at the complete
start method in Code 5.1 and see whether you can understand everything together.

In the last code fragment examined above, a method called startsWith is used. Because that
method is called on the input variable, which holds a String object, it must be a method of
the String class. But what does this method do? And how do we find out?

We might guess, simply from seeing the name of the method, that it tests whether the input
string starts with the word “bye”. We can verify this by experiment. Run the TechSupport
system again and type “bye bye” or “bye everyone”. You will notice that both versions cause
the system to exit. Note, however, that typing “Bye” or “ bye”—starting with a capital letter
or with a space in front of the word—is not recognized as starting with “bye”. This could be
slightly annoying for a user, but it turns out that we can solve these problems if we know a bit
more about the String class.

How do we find out more information about the startsWith method or other methods of the
String class?

5.3 Reading class documentation

The class String is one of the classes of the standard Java class library. We can find out more
details about it by reading the library documentation for the String class.