hw05
fields
recording game results

Part (a)

Due Feb.18 (Mon) as extra credit (optional): only hardcopy is needed.

true or false?: Suppose PizzaServers have a field for their salary. If there are seven PizzaServer objects (instances), then there are seven different boxes labeled “salary” (one inside each object).
For each of the following, indicate whether it's most appropriate to use a field (“f”), a named constant (“nc”), or a local variable (“lv”).
1. A PizzaServer's social security number.
2. the amount of topping on the pizza in a call to crustArea.
3. The total number of hours ever worked by a PizzaServer.
4. The diameter of an Extra-extra-large pizza, at Krusteaze Pizza Korp.
A field is declared inside of , but outside of any .
How many parameters does a setter method have?
How many parameters does a getter method have?
The Java keyword “void” can be used in the place of an actual type when you…
1. declare a parameter
2. specify a method's return type
3. declare a local variable
4. initialize a local variable
(Circle zero or more, appropriately.)

We've been drawing objects on the board as follows (reminiscent of BlueJ's "inspection" window for objects); here's a a before-and-after “snapshot”:

A brand-new PizzaServer:               That same server, after calling:
                                               work(10); 
                                               setSalary(8.0);
                                               work(1);
    PizzaServer                         PizzaServer                 
    +-----------------------+          +-----------------------+  
    |            _________  |          |            _________  | 
    |  salary   |___5.75__| |          |  salary   |___8.0___| | 
    |            _________  |          |            _________  |  
    |  balance  |____0.0__| |          |  balance  |__65.5___| | 
    |              _______  |          |              _______  |  
    |  isManager  |_false_| |          |  isManager  |_false_| | 
    |                       |          |                       |  
    +-----------------------+          +-----------------------+

After sneaking a peek at the first five bullets for part hw05b below...

Draw a picture for a brand new TeamStats object (“before”).
Draw a second, “after” picture of what that same TeamStats object looks like after the two method-calls recordGame(true); recordGame(false);.

Note that the name of the class is above your box, and the variable referring to the object (such as “jo”) is not included in the picture at all.

Part (b)

Due Feb.18 (Mon): As usual, print out the html (via Tools >Project Documentation), and on WebCT attach your .java file.

Test cases will still be in comments, but are now a sequence of statements (since the correct answer can now depend on an object's state). For example, for the tip method from lab05a's PizzaServer, a test sequence would be:

  /** Add a tip directly to this PizzaServer's balance.
   *  @param amt The amount tipped.
   *  
   *  Tests (assuming `ps` is a PizzaServer):
   *     ps.setBalance( 0 ); 
   *     ps.tip( 10 );
   *     ps.getBalance() = 10
   *     ps.tip(  1 );
   *     ps.getBalance() = 11
   *     ps.tip(  0 );
   *     ps.getBalance() = 11  
   */
  void tip( double amt ) {
    this.setBalance( this.getBalance() + amt );
    }

Notice how testing tip requires calling getBalance and setBalance!

Make a new class TeamStats. Include your name in an @author javadoc comment preceding the entire class.
Every TeamStats has three fields: the name of a sports team, the number of games played this season, the number of games won this season.
(Initially, the team will have played no games and will be named “The Nameless Nine”.)
To yourself, confirm that you can create a TeamStats object and inspect it.
For each of the three fields, write the getters and setters (documentation, signatures, then the body).
Test to yourself, that these methods work.
Write a method void recordGame(boolean won), intended to be called once after each game the team plays, which updates the count of games played and (if appropriate) the count of games they've won.
Write the signature and documentation for this function; the body can be entirely empty curly-braces (no return statement is needed ¹, since the function is void). Do not write the body of the method yet.
~~As shown in Friday's lab, use BlueJ to add a test class (right-click on the class) and then …~~ For hw05, your test cases will be just as described above — a series of calls to your method, getters, and setters. (This Tuesday's lab will show us how to make automated test cases.)
Write a method toInfoString(), which returns a string of the form "The Nameless Nine are 2 for 4.", indicating that out of four games, they have won two.

Make a second test-case “testToInfoString”, and call toInfoString two or three times, interspersed with calls to setters and/or recordGame.
Be sure give the expected answers in exactly the form you want, character-for-character. (As always, remember quotation marks (") when writing String literals.)

Part (c)

Due Feb.20 (Wed): implementation (Java code). Turn in hardcopy as usual.

Write the body for recordGame. Click Run Tests to verify that it passes your test cases.
Write the body for toInfoString. Click Run Tests to verify that it passes your test cases.

Your code should use getters and setters, but not access any fields directly ².

Extra Credit

Due with the other work — Sep.24 (documentation & tests) and Sep.26 (implementation).

Write a version of recordGame which accepts two inputs: the team's score and the opposing team's score. Note that this suddenly makes it possible to record ties, which means you might need to add another field to your class.
You can update toString to include this info, if you like.
Write a method winningPercentage which returns a number between 0.0 and 100.0 (inclusive).³ ⁴

¹Note that in a void method it's actually allowable to write “return;” (note the lack of expression before the semicolon). ↩

²except for the getters and setters themselves, of course. ↩

³ If no games have been played, the winning percentage does not exist. In that case it's reasonable to return “not a number” — Double.NaN — which is already the result of 0.0/0.0 (but not the result of 0/0). ↩

⁴Recall that you can convert an int m to a double either by casting — “(double)m” — or by calling functions: “(new Integer(m)).doubleValue()”. (Casting is easier to type, but its syntax is an off-the-wall way to just call a function.) ↩

home—info—exams—lectures—labs—hws
Recipe—Laws—lies—syntax—java.lang docs—java.util docs

©2008, Ian Barland, Radford University
Last modified 2008.Feb.17 (Sun) Please mail any suggestions
(incl. typos, broken links)
to iba�rlandrad�ford.edu

hw05fieldsrecording game results

Part (a)

Part (b)

Part (c)

Extra Credit

hw05
fields
recording game results