Encapsulation: Car – Engine – Wheel

Problem

Model a Car that owns an Engine and 4 Wheels. Practice proper encapsulation: fields should be private, state should only change through controlled methods. A car should start only if the engine is healthy, and should not allow direct mutation of its internal parts.

Requirements

▸Car has a private Engine and private list of Wheels
▸Engine has state: IDLE, RUNNING, OVERHEATED
▸Car.start() — fails if engine is already running or overheated
▸Car.accelerate(speed) — only works when engine is RUNNING
▸Car.stop() — transitions engine back to IDLE
▸Wheel has pressure (psi) — Car.checkTires() returns list of under-inflated wheels (< 30 psi)
▸No public setters that allow bypassing business rules

Constraints

–Do NOT expose raw fields (no public engine, no public wheels[])
–All state transitions must go through methods, not direct assignment

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