$ cat hands-on/payroll-oop.spec HO-04

Area 02 · Object-oriented programming

Department payroll

Pay regular and contractual staff of one department through a common base class, record a payslip for each, and show who supervises whom.

Spec no.: HO-04
Level: Exam-level
Time box: 2 h
Reference: Java · C#
Grading: Self-assessed · rubric is ours, not DICT's

01 Coverage

Area	Sub-skills practised	Role
01 Data manipulation	Validation	Also
02 Object-oriented programming	Abstraction, Encapsulation, Polymorphism, Inheritance, Association, Aggregation, Composition	Primary

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02 Requirements

Abstract Employee with private id and name, abstract kind() and gross(), and deduction() that returns 0 by default.
Regular(id, name, monthly): gross is the monthly salary; deduction is 5% as a practice contribution (not an actual government table).
Contractual(id, name, dailyRate, days): gross is rate × days; days must be 0 to 31.
Composition: each employee owns a list of Payslip(gross, net) objects it creates in issuePayslip(). Expose it read-only.
Association: an employee may have a supervisor, another Employee given by id in the input. Both exist independently.
Aggregation: a Department holds employees by id but does not create them. Reject duplicate ids.
Input lines: R id name monthly [supervisorId] or C id name rate days [supervisorId], until end. On any problem print Skipped: <line>.
Print one line per employee in input order and the department total of net pay.

03 Input and output

Input

R id name monthly [supId]
C id name rate days [supId]
end

Output

Skipped: lines as they are read
id name kind gross x net y [supervisor Name]
Department total net: x.xx

Sample input · stdin

R 1001 Santos 30000
C 2001 Lim 800 22
R 1002 Garcia 25000 1001
C 2002 Uy 800 40
R 1001 Duplicate 1000
end

Expected output · stdout

Skipped: C 2002 Uy 800 40
Skipped: R 1001 Duplicate 1000
1001 Santos   Regular      gross 30000.00  net 28500.00
2001 Lim      Contractual  gross 17600.00  net 17600.00
1002 Garcia   Regular      gross 25000.00  net 23750.00  supervisor Santos
Department total net: 69850.00

Match the sample exactly first, then write at least two test inputs of your own.

04 Edge cases to test

Days above 31
A duplicate id
A supervisor id that does not exist yet
A negative salary

05 Starter outline and hints

Outline

Payslip(gross, net) — created only inside Employee
abstract Employee { private id, name, supervisor, payslips; issuePayslip() }
Regular, Contractual extend Employee
Department { map id → Employee; add rejects duplicates }
parse lines → add; then for each: issuePayslip, print, total

Hints

Hint 1

Composition: the part's lifetime is tied to the whole. Aggregation: the whole only refers to parts that live elsewhere.

Hint 2

A LinkedHashMap / Dictionary plus an insertion-ordered list keeps input order and fast lookup.

06 Practice rubric

Criterion	Sub-skills	Look for	Pts
Abstraction and inheritance	AbstractionInheritance	Abstract base; subclasses supply only their pay rule.	20
Polymorphism	Polymorphism	No type checks in the payroll loop.	15
Encapsulation	Encapsulation	Private fields, validated constructors, read-only payslip list.	15
Relationships	AssociationAggregationComposition	Payslips composed, supervisor associated, department aggregating; you can explain the difference.	30
Correct pay and validation	Validation	Totals match the sample; bad lines skipped.	20
Total			100

Our own weighting for practice. It is not the DICT scoring scheme.

07 Self-check

Tick only what you have verified by running your own program.

I can say in one sentence each why payslips are composition, the department is aggregation and the supervisor is association.
The payroll loop has no if or switch on the employee type.
Code outside Employee cannot add to the payslip list.
The total for the sample is 69850.00.
Adding an Hourly type would need only a new subclass.

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08 Reference solution

Both versions compiled and reproduced the sample output on Java 21 and .NET 8 when this site was built. Reference solutions are in Java and C#. The 2023 FAQ copy also lists C, C++ and Visual Basic 6.0 / .NET; the same structure carries over, but you will need your language's own file and database APIs.

Try the whole brief first. The reference is one correct approach, not the only one, and reading it early removes most of the practice value.

09 Exam-day habits

Work without internet search to simulate exam conditions.
Type the sample input yourself and compare your output line by line before you look at the reference.