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

Question

IT Interview Practice · 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.

Mengapa punika wigati

Patest klasik

Kahanan mencolok

Mengapa punika wigati

Pitakon sing gegandhengan