COMP1210 Project 3 Solution

Files to submit to Web-CAT:
• ExpressionEvaluator.java
• MealOrder.java

Specifications
Overview: You will write two programs this week. The first will compute the value generated by a specified expression and the second will read data for a meal order and then interpret and print the formatted meal order information.

• ExpressionEvaluator.java


!|𝟏. 𝟐𝒙𝟑 − 𝟏𝟎𝒙 (𝟓𝒙𝟒 − 𝟕𝒙𝟑)𝟐
𝟐 + 𝟏𝟎)
(𝒙

Next, determine the number of characters (mostly digits) to the left and to the right of the decimal point in the unformatted result. [Hint: You should consider converting the type double result into a String using the static method Double.toString(result) and storing it into a String variable. Then, on this String variable use the indexOf(".") method from the String class to find the position of the period (i.e., decimal point) and the length() method to find the length of the String. Knowing the location of the decimal point and the length, you should be able to determine the number of digits on each side of the decimal point.]

Finally, the result should be printed using the class java.text.DecimalFormat so that to the right of the decimal there are at most four digits and to the left of the decimal each group of three digits is separated by a comma in the traditional way. Also, there should also be at least one digit on each side of the decimal (e.g., 0 should be printed as 0.0). Hint: Use the pattern "#,##0.0###" in your DecimalFormat constructor. However, make sure you know what this pattern means and how to modify and use it in the future.

Design: Several examples of input/output for the ExpressionEvaluator program are shown below.

Line # Program output
1
2
3
4
5 Enter a value for x: 0
Result: 0.1
# of characters to left of decimal point: 1
# of characters to right of decimal point: 1 Formatted Result: 0.1


Line # Program output
1
2
3
4
5 Enter a value for x: 10.5
Result: 438.0203717219859
# of characters to left of decimal point: 3
# of characters to right of decimal point: 13 Formatted Result: 438.0204

Line # Program output
1
2
3
4
5 Enter a value for x: -10.5
Result: 572.7958155057314
# of characters to left of decimal point: 3
# of characters to right of decimal point: 13 Formatted Result: 572.7958

Line # Program output
1
2
3
4
5 Enter a value for x: 123456
Result: 7.620605543800056E10
# of characters to left of decimal point: 1
# of characters to right of decimal point: 18 Formatted Result: 76,206,055,438.0006
When the characters to the right of the decimal in the unformatted result end with E followed by one or more digits (e.g., E10 indicates an exponent of 10), the ‘E’ should be included in the count of the characters to the right of the decimal point.

Code: In order to receive full credit for this assignment, you must use the appropriate Java API classes and method to do the calculation and formatting. It is recommended as a practice that you do not modify the input value once it is stored.

Test: You will be responsible for testing your program, and it is important to not rely only on the examples above. Assume that the amount entered can be any positive or negative floating-point number.



• MealOrder.java

Requirements: The purpose of this program is to accept coded information as input that includes the number of adult meals, price of adult meal, number of child meals, price of child meal, and name of the customer. Orders of $100 or more receive a 15% discount (see constants on page 5). The program should then print the user's order information including the total, as well as a "lucky number" between 1 and 99999 inclusive. If the order is less than $100, total is printed; otherwise subtotal, discount, and total are printed. The coded information is formatted as follows:

021250040625Pat John

name

price per child meal (note the assumed decimal point) number of child meals
price per adult meal (note the assumed decimal point) number of adult meals
Whitespace before or after the coded information should be disregarded (e.g., if the user enters spaces or tabs before the coded information then the spaces should be disregarded). Your program will need to print the customer’s name, number of adult meals, price per adult meal, number of child meals, price per child meal. If order is less than $100, total is printed; otherwise, subtotal, discount, and total are printed. Finally, a random “lucky” number in the range 1 to 99999 is printed. If the user enters a code that does not have at least 12 characters, then an error message should be printed. [For this assignment, the first 12 characters, if present, will need to be digits; otherwise a runtime exception will occur.]

Design: Several examples of input/output for the program are shown below.

Line # Program output
1
2(blank)
3
4 Enter your order code: 123456789

Invalid Order Code.
Order code must have at least 12 characters.


Note that the code below has five leading spaces.
Line # Program output
1
2(blank)
3
4
5
6
7 Enter your order code: 021250040625Pat John
Name: Pat John
Adult meals: 2 at $12.50
Child meals: 4 at $6.25
Total: $50.00
Lucky Number: 68408


Line # Program output
1
2(blank)
3
4 5
6
7
8 9 Enter your order code: 241495000000Sam Smith

Name: Sam Smith
Adult meals: 24 at $14.95
Child meals: 0 at $0.00
Subtotal: $358.80
15% Discount: -$53.82 Total: $304.98
Lucky Number: 35344


Line # Program output
1
2(blank)
3
4
5 6
7 Enter your order code: 021500120500Penny's Party

Name: Penny's Party
Adult meals: 2 at $15.00
Child meals: 12 at $5.00
Total: $90.00
Lucky Number: 28930


Line # Program output
1
2(blank)
3
4
5 6
7 Enter your order code: 202500501000Jackie's Big Party

Name: Jackie's Big Party
Adult meals: 20 at $25.00
Child meals: 50 at $10.00
Subtotal: $1,000.00
15% Discount: -$150.00
Total: $850.00
Lucky Number: 02304


Code: In order to receive full credit for this assignment, you must use the appropriate Java API classes and methods to trim the input string, to do the extraction of the substrings, conversion of substrings of digits to numeric values as appropriate, and formatting. These include the String methods trim, charAt, and substring, as well as wrapper class methods such as Integer.parseInt and Double.parseDouble which can be used to convert a String of digits into a numeric value. The dollar amounts should be formatted so that both small and large amounts are displayed properly, and the prize number should be formatted so that five digits are displayed including leading zeroes, if needed, as shown in the examples above. It is recommended as a practice that you not modify input values once they are stored. While not a requirement, you should consider making the student discount and faculty/staff discount constants. For example, the following statements could be placed above the main method.
static final double DISCOUNT = 0.15; static final double DISCOUNT_THRESHOLD = 100.0;

Test: You are responsible for testing your program, and it is important to not rely only on the examples above. Remember, when entering standard input in the Run I/O window, you can use the up-arrow on the keyboard to get the previous values you have entered. This will avoid having to retype the meal order data each time you run your program.

Grading
Web-CAT Submission: You must submit both “completed” programs to Web-CAT at the same time.
Prior to submitting, be sure that your programs are working correctly and that they have passed Checkstyle. If you do not submit both programs at once, Web-CAT will not be able to compile and run its test files with your programs which means the submission will receive zero points for correctness. I recommend that you create a jGRASP project and add the two files. Then you will be able to submit the project to Web-CAT from jGRASP. Activity 1 (pages 5 and 6) describes how to create a jGRASP project containing both of your files.

Hints
MealOrder.java

1. The meal order code should be read in all at once and stored in a variable of type String, after which the individual values should be extracted using the substring method.
2. The String value for the number of meals should be converted to type int (using Integer.parseInt) so that it can be used in calculations.
3. The String value for price values should be converted to type double (using Double.parseDouble) so that it can be used in calculations.
4. Use an if-else statement to print total versus subtotal, discount, total. That is, convert the following pseudo code into Java:
if total is less than DISCOUNT_THRESHOLD print total
else print subtotal, discount, and total.
5. An appropriate DecimalFormat object should be created using the pattern "$#,##0.00" so that its format method can be called when printing the values for meal prices, subtotal, discount, and total for proper formatting.