Apa bedane antarane hubungan is-a lan has-a?

Question

Accepted Answer

**Is-a** iku hubungan *tipe* — dimodelake kanthi **inheritance** (sawijining `Car` *iku* `Vehicle`). **Has-a** iku hubungan *pangandhelan* — dimodelake kanthi **composition** (sawijining `Car` *duwe* `Engine`). Milih ingkang tenggak iku putusan modeling inti.

## Mengapa punika wigati

```java
// IS-A → inheritance
class Vehicle { void move() {} }
class Car extends Vehicle { }        // a Car IS A Vehicle

// HAS-A → composition
class Engine { void start() {} }
class Car2 {
    private Engine engine = new Engine();   // a Car HAS AN Engine
    void start() { engine.start(); }        // delegate to the part
}
```

## Patest klasik

Panjaluk: "Apa X *jenis saka* Y, utawa X *duwe/nggunakake* Y?"

```text
A Dog        IS-A Animal        → inheritance ✅
A Car        HAS-A Engine       → composition ✅
A Square     IS-A Shape         → inheritance ✅
A Manager    HAS Employees      → composition (a list) ✅
A Stack      HAS-A list (not IS-A) → composition (see earlier pitfall) ✅
```

## Kahanan mencolok

Wonten tiyang sing nyedhak inheritance kanggo *ngulang-ulang kode*, sanajan hubungane pancen has-a. Yen punika ora bakal ngganti subclass kanggo basis ing endi-endi, asale ora is-a — gunakakake composition.

## Mengapa punika wigati

Pedafaran iki iku panjaluk keputusan praktis ana mburine "favor composition over inheritance": pilih hubungan ingkang leres, dudu ingkang nyiksa saweneh baris.

Nggawe ing tenggak ndhudhuk hierarki cekak lan jujur, lan njegog pelanggaran Liskov dene "subtype" ora bisa manggon kanggo indukan.