diff --git a/README.md b/README.md index 4f153b0..e8eb268 100644 --- a/README.md +++ b/README.md @@ -17,12 +17,16 @@ Work through all these exercises. You edit this file with your answers for these ### Exercise 2.2 * What value is returned if you check the machine’s balance after it has printed a ticket? +Answer: The balance will be 0 ### Exercise 2.3 * Experiment with inserting different amounts of money before printing tickets. * Do you notice anything strange about the machine’s behavior? * What happens if you insert too much money into the machine – do you receive any refund? + Answer: The machine will keep the money if too much money is inserted. There will be no refund +Answer: * What happens if you do not insert enough and then try to print a ticket? +Answer: The tickets will still be printed ### Exercise 2.4 * Try to obtain a good understanding of a ticket machine’s behavior by interacting with it on the object bench before we start looking at how the `TicketMachine` class is implemented in the next section. @@ -31,6 +35,7 @@ Work through all these exercises. You edit this file with your answers for these * Create another ticket machine for tickets of a different price. * Buy a ticket from that machine. * Does the printed ticket look different? + Answer: No, the only difference would only be the price of the ticket. Tickets are still being printed regardless of how much money is being inserted. ### Exercise 2.6 * Write out what you think the outer wrappers of the `Student` and `LabClass` classes might look like – do not worry about the inner part. @@ -41,11 +46,15 @@ Does it matter whether we write
or
`class public TicketMachine`
in the outer wrapper of a class? +Answer: Yes, only the latter works. * Edit the source of the `TicketMachine` class to make the change and then close the editor window. * Do you notice a change in the class diagram? + Answer; You can no longer create an object out of the class diagram * What error message do you get when you now press the compile button? + Answer: "Error(s) found in class. Press Command K or click link on right to go to next error." * Do you think this message clearly explains what is wrong? + Answer: Yes ### Exercise 2.8 * Check whether or not it is possible to leave out the word `public` from the outer wrapper of the `TicketMachine` class. @@ -54,9 +63,13 @@ in the outer wrapper of a class? * From your earlier experimentation with the ticket machine objects within BlueJ you can probably remember the names of some of the methods – `printTicket`, for instance. * Look at the class definition in Code 2.1 and use this knowledge, along with the additional information about ordering we have given you, to try to make a list of the names of the fields, constructors, and methods in the `TicketMachine` class. * Hint: There is only one constructor in the class. - + Answer: Fields: Price, Balance, and Total + constructor: Ticket machine + Methods: getPrice, getTicketNumber, getBalance, ### Exercise 2.10 * Do you notice any features of the constructor that make it significantly different from the other methods of the class? +Answer: Constructors is the only method with a parameter, responsible for assigning the values of price, balance, total, and ticketNumber. Also the constructor does not return any types of values + ### Exercise 2.11 * What do you think is the type of each of the following fields? @@ -66,6 +79,7 @@ private int count; private Student representative; private Server host; ``` +Answer = int, Student, Server ### Exercise 2.12 * What are the names of the following fields? @@ -75,6 +89,7 @@ private boolean alive; private Person tutor; private Game game; ``` +Answer = alive, tutor, game ### Exercise 2.13 In the following field declaration from the TicketMachine class
@@ -83,35 +98,42 @@ In the following field declaration from the TicketMachine class
private int price; ``` does it matter which order the three words appear in? +Answer: Yes * Edit the `TicketMachine` class to try different orderings. After each change, close the editor. * Does the appearance of the class diagram after each change give you a clue as to whether or not other orderings are -possible? +possible? Yes * Check by pressing the compile button to see if there is an error message. * Make sure that you reinstantiate the original version after your experiments! ### Exercise 2.14 * Is it always necessary to have a semicolon at the end of a field declaration? +Answer: Yes, as semicolon tells you the end of your declaration. * Once again, experiment via the editor. * The rule you will learn here is an important one, so be sure to remember it. ### Exercise 2.15 * Write in full the declaration for a field of type `int` whose name is `status`. +Answer: private int status ### Exercise 2.16 * To what class does the following constructor belong? ``` public Student(String name) ``` +Answer: Student ### Exercise 2.17 * How many parameters does the following constructor have and what are their types? ``` public Book(String title, double price) ``` +Answer: 2 parameters ### Exercise 2.18 * Can you guess what types some of the `Book` class’s fields might be? * Can you assume anything about the names of its fields? +Answer: Some of the names that can be included in the fields would be Genre, Price, and Title + READ upto and INCLUDING section 2.15 of this chapter. diff --git a/TicketMachine.java b/TicketMachine.java index 630c4ea..a60d011 100644 --- a/TicketMachine.java +++ b/TicketMachine.java @@ -9,10 +9,11 @@ * @author David J. Barnes and Michael Kolling * @version 2008.03.30 */ -public class TicketMachine +public class TicketMachine + { // The price of a ticket from this machine. - private Integer price; + private Integer price; // The amount of money entered by a customer so far. private Integer balance; // The total amount of money collected by this machine.