Apa dene Java access modifiers?

Question

Accepted Answer

**Access modifiers** ngontrol **visibility** saka kelas, metode, lan field — sapa sing bisa ngakses. Iki mekanisme di balik encapsulation. Java duwe patang level, saka paling restriksi nganti paling ora restriksi.

## Patang level

```java
public class Example {
    public int a;        // accessible from ANYWHERE
    protected int b;     // same package + SUBCLASSES (even in other packages)
    int c;               // package-private (DEFAULT, no keyword) — same package only
    private int d;       // accessible ONLY within THIS class
}
```

## Tabel visibility

```text
Modifier      Same class  Same package  Subclass (other pkg)  Everywhere
────────────────────────────────────────────────────────────────────────
public            ✓            ✓                ✓                  ✓
protected         ✓            ✓                ✓                  ✗
(default)         ✓            ✓                ✗                  ✗
private           ✓            ✗                ✗                  ✗
```

Catatan: nglirwakake modifier menehi **package-private** (default) — katon ing paket sing padha wae. Iki level sing beda, ora padha karo public.

## Carane ngaktifake encapsulation

```java
public class BankAccount {
    private double balance;          // hidden — protect the data

public void deposit(double amt) { // public API — controlled access
        if (amt > 0) balance += amt;
    }
    public double getBalance() {      // read-only access to private data
        return balance;
    }
}
// outside code CANNOT do account.balance = -1000 (it's private)
```

Pola standar: gawe field **`private`** lan buka metode **`public`** sing dikontrol. Iki nglindhungi invariant lan ngidini owah internal representation tanpa mecah pemanggil — esensi saka encapsulation.

## Panduan praktis

```text
✓ Fields → private (almost always); expose via methods if needed
✓ Public API methods → public
✓ Internal helpers → private
✓ For subclasses to access/override → protected
✓ Classes → public (usable anywhere) or package-private (internal to a module)
```

Prinsip: gawe modifier **paling restriksi** sing isih bisa dianggo (least privilege) — diwiwiti private lan buka mung yen kudu.

## Mengapa iku penting

Access modifiers iku carane Java nglaksanakake **encapsulation** — prinsip OOP dhasar nglindungi detail internal lan mbukak interface sing dikontrol.

Nemtokake modifier sing bener (default `private` kanggo field, `public` mung kanggo API sing dituju) nglindungi integritas data, nyegah kode luar gumantung ing internal (dadi bisa refactor bebas), lan nggawake penggunaan kelas sing dituju jelas.

Pamahaman kabeh patang level — luwih-luwih default package-private sing asring terlali lan `protected` sing manjang subclass — penting kanggo ngrancang kelas lan API sing kapsulan apik, terpelihara, lan kontrol carane kodene dibukak marang sistem liyane.