Java Practice

Price parcels from the depot's rate card in whole numbers: a box's volumetric weight, the chargeable kilos rounded up, a yearly forecast that does not overflow, and a price label in euros.

Decide what each kind of parcel costs and whether the depot can take it, with a switch over a sealed interface of records and rules checked in a defined order.

Plan a delivery van's day from its stops: parcels per zone in alphabetical order, express stops first, and the loading order that puts the last stop in first, without changing the list you are given.

Make a tracking number that cannot exist in a bad state: a record that checks its country and number, reads text like DE-004211 with a flexible constructor, prints itself back the same way, and checks text without throwing.

Model a parcel's journey as an enum: readable labels, final statuses, the moves each status allows, refused jumps, and a count of every status in declaration order.

Keep business accounts inside their credit limit: an interface with a default method, a class whose balance only changes through its methods, a checked exception that says how far over a charge went, and an Optional lookup by id.

Turn the depot's delivery rules into small pieces of code you can pass around: a lambda for late deliveries, rules joined with and, a ranking built from method references, and the worst delay of the week through an Optional.

Answer the zone leads' weekly questions with collectors: revenue per zone in alphabetical order, the late parcels of every zone, late against on time, and the latest delivery day per zone.

Follow the depot's numbers day by day: every stop on every route once, a running revenue total, rolling late counts, weekly totals that keep a short last week, and the clean start before the first late day.