Apa iku enkapsulasi?

Question

Accepted Answer

**Enkapsulasi** ngrupa data lan method sing nindakake operasi ing dalem siji unit (kelas) lan **ndhelikke internal state** ing ndalem interface publik sing dikontrol. Panggilan interact lumantar method, ora nggatali field langsung.

## Kenapa ndhelikke state

Yen sapa wae bisa ngowahi field langsung, sampeyan ora bisa njamin obyek tetep valid. Enkapsulasi ngidini kelas **ndakoake invariant dewe-dewe**.

```java
public class Account {
    private double balance;             // hidden: no direct access

public void withdraw(double amount) {
        if (amount <= 0)                // guard the invariant
            throw new IllegalArgumentException("amount must be positive");
        if (amount > balance)
            throw new IllegalStateException("insufficient funds");
        balance -= amount;              // only valid changes get through
    }

public double getBalance() { return balance; }
}
```

```java
// Without encapsulation, this would be possible and disastrous:
account.balance = -5000;   // bypasses every rule
```

Kabeh `balance` iku pribadi, siji-sijine cara kanggo owahi katelu `withdraw`, sing nglindungi aturan.

## Jebakan

Enkapsulasi dudu "nambah getter/setter kanggo saben field". Ndhelikke setter kanggo kabeh barang rasane luwih becik tinimbang public field. Ndhelikke *prilaku*, ora state mentah.

## Kenapa dina penting

Enkapsulasi njaga invariant ing siji panggonan, mulane bug ing nangani keseimbangan mung bisa ana ing `Account`, ora nyebar ing kabeh codebase.

Iku uga ngidini sampeyan ngganti internal representation mengko (nyimpen cent minangka integer, nambahe logging) tanpa mrusak panggilan, amarga mung gumantung ing interface publik.