Objects First With Java - Solutions - Easy semester!

|Exercise 2.2 |
|Zero. |
|Exercise 2.3 |
|If too much money is inserted the machine takes it all - no |
|refund. |
|If there isn't enough money inserted, it still prints out the |
|ticket. |
|Exercise 2.5 |
|It looks almost completely the same. Only the price on the ticket |
|is different. |
|Exercise 2.6 |
|The outer part of the student class: |
| |
|public class Student |
|{ |
|} |
| |
|The outer part of the LabClass class: |
| |
|public class LabClass |
|{ |
|} |
|Exercise 2.7 |
|Yes, the order of public and class matters. |
|Exercise 2.8 |
|It is possible to leave out the word public. |
|Exercise 2.9 |
|It is not possible to leave out the word class. |
|Exercise 2.10 |
| |
|Fields: |
|price |
|balance |
|total |
|Constructors: |
|TicketMachine |
|Methods: |
|getPrice |
|getBalance |
|insertMoney |
|printTicket |
|Exercise 2.11 |
| |
|It does not have any return type. The name of the constructor is |
|the same as the name of the class. |
|Exercise 2.12 |
| |
|int |
|Student |
|Server |
|Exercise 2.13 |
| |
|alive |
|tutor |
|game |
|Exercise 2.14 |
|Student, Server, Person and Game |
|Exercise 2.15 |
| |
|The exact order matters. |
|Exercise 2.16 |
| |
|Yes, it always necessary to have a semicolon after a field |
|declaration. |
|Exercise 2.17 |
|private int status; |
|Exercise 2.18 |
|It belongs to the class Student. |
|Exercise 2.19 |
|It has two parameters. One is of type String and the other of type|
|double. |
|Exercise 2.20 |
|It would be reasonable to expect the types to be the same as the |
|two parameters (String and double). |
|Can't really assume anything about the names, but probably |
|something like title and price. |
|Exercise 2.21 |
|name = petsName; |
|Exercise 2.22 |
|public Date(String month, int day, int year) |
|Exercise 2.23 |
| |
|Aside from their names, the only difference is that getPrice() |
|returns the value of the price field whereas getBalance() returns |
|the value of the balance field. |
|Exercise 2.24 |
| |
|How much money have I inserted into the machine? |
|Exercise 2.25 |
| |
|No. There is no direct link between the name of a method and the |
|name of the field. However, it is a convention to use a name for |
|the method that clearly links it to the field. |
|Exercise 2.26 |
|public int getTotal() |
|{ |
|return total; |
|} |
|Exercise 2.27 |
| |
|Missing return statement. |
|Exercise 2.28 |
| |
|The header for getPrice() has an int as return type. |
|The header for printTicket() has void as return type. |
|Exercise 2.29 |
| |
|No. |
|Because they don't need to return anything. |
|Yes. Both headers have void as return types. |
|Exercise 2.31 |
|It has a return type (void) and constructors do not have return |
|types. It also does not have the same name as the class it is in. |
|Exercise 2.32 |
|price = cost; |
|Exercise 2.33 |
|score = score + points; |
|Exercise 2.34 |
|It is a mutator. |
|Use an inspector to view the current score, then call the increase|
|method with a positive parameter value and observe that score |
|increases by that value. |
|Alternatively, if score has an accessor method; call the accessor,|
|then call increase, and then call the accessor once again to |
|verify that it returns the updated value, indicating that the |
|field has been modified. |
|Exercise 2.35 |
|price = price - amount; |
|Exercise 2.36 |
|Note that no quote marks are printed, just the following: |
| |
|My cat has green eyes. |
|Exercise 2.37 |
|public void prompt() |
|{ |
|System.out.println("Please insert the correct amount of money."); |
|} |
|Exercise 2.38 |
| |
|Instead of printing out the actual price of the ticket, it |
|displays the word "price": |
| |
|# price cents. |
|Exercise 2.39 |
|