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hw05
Modifying objects
Student gpas
due in class Oct.16 (Tue)
For this homework,
modify the exercises for class Student
(started in labs
6a,
6b,
and
7a),
so that it stores not the gpa (derived info),
but rather a student's total number of (weighted) grade-points.
(We discussed this in lab07b—Mutation, continued: considering data representation; hw05 time.)
(Start with whatever work you completed with your partner in lab,
but if you weren't finished you must add to it yourself.
If you don't have access to their work, you can
just re-write it — once the concepts are understood,
the mechanics of writing the class should be straightforward.)
Each function beside the constructor must include test cases,
and also javadoc documentation
(@param and @return tags as appropriate).
Of course, the start of your file should include acknowledgements of
everybody who contributed code.
In particular, your code must have:
- (3pts) a class Student
which keeps track of a name, id, major, hours completed,
and
different from lab:
gradepoints earned
(but not a field for the gpa).
- (3pts) a constructor which takes in a value for each field
and initializes it; do not call super.
- (5pts) a function
different from lab:
getGPA,
which takes in a Student and returns their gpa.
-
(3pts)
A method onDeansRoll which takes in a
Student,
and returns whether
the student currently qualifies for the dean's roll:
a gpa above 3.6.
- (4pts) a function enrollNewStudent
which takes in
just a student's name
and id,
and returns a new Student object with
no hours completed, the major "Undeclared",
different from lab:
and no gradepoints.
- (5pts) a function setMajor,
which takes in a
Student
and a String,
and changes that student's major to the indicated string.
(with no return — a void method).
- (5pts) a function toPrettyString,
which takes in a Student and
returns a string suitable for non-programmers to read:
including the student's
name, major, gpa1, and hours-completed
(but not their total-grade-points).
(6pts) a method recordGrade
which takes in a Student,
a letter-grade from a class,
and a number of credit hours the class was worth;
the method doesn't return any information,
but it
updates the Student's information accordingly.
Be sure to write two test cases first, and
think carefully about what information gets udpated!
You don't need to worry about +/- grades, and to make life easy you
can use 'E' to represent a failing grade if
you like, although it would be nice to properly allow 'F'.
You don't need to include other methods mentioned in the lab pages
— e.g. onDeansRoll etc.,
but if you already have them, sure keep them there!
Your test cases can all be in one function, so that
you can have a few local variables to store some Students,
and re-use them for multiple tests.
Be careful, now that we are changing (mutating) objects over time:
you can no longer swap the order of your test cases, w/o changing
the expected (“desired”) results!
You can use assertEquals (from previous hw) for your test cases.
To test that your void methods work,
you have first call that mutating function,
and then afterwards assert that the updated field really does have the
desired value.
// Note: this is what some of my examples/test cases looked like; yours
// might be slightly different depending on how you declared your fields/constructor.
Student stu1 = new Student( "Troy Ilium", "MATH", 30, 90 );
setMajor( stu1, "ANTH" );
assertEquals( stu1.major, "ANTH" );
|
Alternately, you could also assert that all the fields
of stu1 look the way you expect them to
(testing/checking that your method didn't change fields that
should have stayed the same!):
assertEquals( stu1, new Student("Troy Ilium", "ANTH", 30, 90) );.
Note that if you want two students with entirely-equal-fields to
be counted as equal, you need to be sure to extend Object120.
1
It's okay if your gpa prints with many decimal places.
If you really want
to convert the double into a String
obeying a certain format,
You can use the static method format that
lives inside class String.
For example, in code pad try evaluating
“String.format( "hello: %8.3f bye", 123.456789 )”.
(The "3" means “3 places after the decimal”,
the "8" means “8 characters wide total
(padded with leading spaces)”,
and the "f" means “floating-point or double”.
See
the docs
(clicking the link on 'format string' for more info on that).
↩
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