I have pulled up quite a few websites trying to explain.. if, else, switch statements.
I am having a difficult time placing it in code.
I have a project - Below are the instructions to the program and what I've formulated so far.
Do I have to define A,B,C,D before putting it in the switch statement? What am I missing?
Project Objectives:
• To develop skills in using the
Java selection constructs (if, if else, and switch),
• To further explore some of the
String class's capabilities
• To look at displaying the attributes of an object
• To become familiar with basic UML class diagrams
Prep Readings:
Big Java textbook, Chapters 1 - 5.
Background Information:
The Unified Modeling Language (UML) provides a useful notation for designing and developing object-oriented software systems. One of the basic components of the UML is a class diagram, which are used to depict the attributes and behaviors of a class. A basic class diagram (as shown in the figure below) has three components. The first is the class name. The second component includes the class's attributes or fields. Each attribute is followed by a colon (
and its data type. The third component includes the class's behaviors or methods. If the method takes parameters, their types are included in parentheses. Each behavior is also followed by a colon (
and its return type. If the return value of a method is void, the return type can be omitted. For more information on the UML, refer to
http://www.uml.org/.
Project Requirements:
1. We are going to develop a simple class that represents a pay-per-view movie customer and determines the cost of watching a movie using Fox Cable Company's pay-per-view movie service, based on the movie's ratings and whether it is a new release or a rare movie. For example, the movie "The Departed" has a rating of A, and since it is a new release, the movie will cost extra. The movie "Howard the Duck" has a rating of F, and since it is a rare movie, it will cost extra as well. The Viewer class represents an individual customer who purchased a pay-per-view movie.
2. Design and build a Viewer class. The class will have three instance fields (or instance variables as they are also called). There will be a customer variable that will hold the customer's name. The class will also have a movieCode variable that will store the quality of movie based on its rating and whether it is new or rare. Finally, a cost variable that will store the total cost for the movie. This class should have a parameterized constructor, accessor methods for the instance fields, a method to compute the cost of the movie, a method to update the movie's rating, and a method to convert the state of the object to a String. Using the UML, the class diagram for the Viewer class looks like this:
Viewer
Customer : String
movieCode : String
cost : double
Viewer(String, String)
getCustomer() : String
getMovieCode() : String
getCost() : double
computeCost()
updateMovieCode(String)
toString(): String
• The constructor will assign the first parameter to the variable customer and the second to the movieCode variable. The constructor will then call computeCost() to convert the movie code to the numeric cost and store it in cost variable.
• The class will have three accessor methods getCustomer(), getMovieCode(), and getCost(). Each will return the value of the respective instance variable.
• The method computeCost() handles the conversion of the movie code to cost and saves it in the instance variable cost. Movie codes consist of a rating letter (A, B C, D, or F) and an optional character (N or R) to identify if the movie is a new release or rare. The base price of a movie is $3.95. The price of the movie increases as the quality of movie increases according to the table below:
Movie Rating Price Factor
A 1.50
B 1.36
C 1.26
D 1.06
F 1.00
• The optional movie modifier can have one of two possible values to indicate whether the movie is new (N) or the movie is rare (R). A rare movie adds $1.00 to the base price, while a new movie adds $2.50 to the base price. Note that F list movies always have a rare (R) modifier. For example, a movie code value of "A"(no modifier) would cost 3.95 * 1.50 = $5.93, a movie code value of "AN" would cost (3.95 + 2.50) * 1.50 = $9.65, and a movie code value of "BR" would cost (3.95 + 1.00) * 1.36 = $6.73
You must use the switch statement to determine the proper price factor using the ratings, and use the if else construct to handle the movie modifiers.
• The class will have a method updateMovieCode (String) that takes a new movie code and updates the movieCode and cost variables accordingly. Use the computeCost() method to update the cost. Note that we can call methods of a class from within the class; in this case, we do not use the dot (.) operator. Methods which are useful to other methods are called utility methods, and do not need to be public if they will only be called from within the class. The computeCost() method is a utility method, and should be defined as a private method.
• The method toString() allows us to access the state of the object in a printable or readable form. It converts the variables to a single string that is neatly formatted. Look at pages 161 -162 of the text for a discussion of escape sequences. These are characters that you can insert into your strings and, when printed, will format the display neatly. You can insert an escape sequence for the tab character and get a tabular form when printing. This tab character is '\t'. Your class will have a toString() method that concatenates customer, movieCode and cost separated by tab characters and returns this new string. When you try to print an object, thetoString() method will be implicitly called. For example, if John Snow watched a movie that had a movie code value of "DR", the output would be:
John Snow DR $5.24
3. Build a class ViewerTest that will
test the constructor and all the public methods of the Viewer class. Generate objects that have each of the possible values for a movie code and print each object by implicitly calling the toString() method on each object. Note that there will be 13 valid movie codes since the movie modifier is optional and an F rating always has the rare (R) modifier (A, AN, AR, B, BN, BR, C, CN, CR, D, DN, DR, and FR). Remember to test for invalid movie codes as well (for example, G, BA, H3, etc). Invalid movie codes should display an error message and set the cost to $9999.99. Your program should ignore case in movie code values. For example, a movie code value of "an" should be processed the same as "AN".
Implementation Notes:
•
You should use both the switch and the if else constructions in this program. The switch construction is good when you are checking a single variable against a number of different discrete values. A character variable (char) is discrete (you have one of a set of characters only) as are integral types (int). Strings and floating-point numbers are not discrete and will not work with the switch statement. if statements can be used anytime you have a relational operation such as equality, less than, etc. But you need to be careful when using a long series of if {...} else {...} constructs because of the confusion factor (Which if does this else go with? Where am I in this sequence of tests?).
• Strings have many behaviors or methods available. These behaviors include finding an individual character in the string, telling how many characters are in the string and converting the contents of the string to either upper or lower case. You will need to use the charAt(int i) method to extract the movie rating and movie modifier from the movieCode string to work with. For example, suppose you have a Java statement:
String x = "This is a string.";
You can extract the period at the end of the statement by using the Java statement:
char period = x.charAt(16);
This will extract the 17th character in the string and place it in the variable period. Remember that string numbering starts at 0, not 1. A better way to do this would be to use the length()method of the String class, which tells us how many characters are in the string. So we can use it to tell us where the period is since we know it is the last character (in this specific case) in the string. So the Java statement:
int howLong = x.length();
tells us the number of characters. But the numbering starts at zero, so if we want to access the last character, we have to reduce howLong by 1. Then we could do:
char period = x.charAt(howLong - 1);
to get the same result as in the second statement above.
Experienced programmers would probably simplify the construction slightly more by eliminating the variable howLong if this is the only use of it. We could then re-write it as:
char period = x.charAt(x.length() - 1);
Note how we are nesting method calls inside of other method calls. This can be a very powerful programming technique.
You should also use the toUpperCase()method of the String class to convert the movie code to upper case characters before processing it. For example, you should convert the movie code "an" to "AN." If you do this when the value is first stored in the object, you only have to process upper case characters in your computeCost()method.
