Piye carane enum bisa gawé ing Java?

Question

Accepted Answer

**enum** nemtokake tipe karo **tetapan jenengan sing wis ditétepake**. Enum Java luwih kuwat tinimbang daftar tetapan prasaja ing basa liya — iku kelas sing lengkap bisa duwe medan, konstruktor, lan metode.

## Enum dasar

```java
public enum Day {
    MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY, SUNDAY
}

Day today = Day.MONDAY;

// works great in switch
switch (today) {
    case MONDAY -> System.out.println("start of week");
    case SATURDAY, SUNDAY -> System.out.println("weekend");
    default -> System.out.println("weekday");
}
```

Enum nyediyake **keamanan tipe** — `Day today = Day.MONDAY` mung bisa nampung nilai `Day` sing sah, ora kaya nggunakake integer utawa string sebarang minangka tetapan (sing ngidini nilai ora sah lan kasalahane ketik).

## Metode enum sing wis ana

```java
Day.MONDAY.name();        // "MONDAY"
Day.MONDAY.ordinal();     // 0 — position in the declaration
Day.values();             // array of all constants (iterate them)
Day.valueOf("FRIDAY");    // get a constant by name
for (Day d : Day.values()) { ... }   // iterate all values
```

## Enum karo medan, konstruktor, lan metode (bagean sing kuwat)

```java
public enum Planet {
    MERCURY(3.3e23, 2.4e6),    // each constant calls the constructor with arguments
    EARTH(5.97e24, 6.37e6),
    JUPITER(1.9e27, 7.1e7);

private final double mass;       // enums can have FIELDS
    private final double radius;

Planet(double mass, double radius) {   // constructor (implicitly private)
        this.mass = mass;
        this.radius = radius;
    }
    public double surfaceGravity() {        // and METHODS
        return 6.67e-11 * mass / (radius * radius);
    }
}

Planet.EARTH.surfaceGravity();   // compute using EARTH's data
```

Saben tetapan enum yaiku instansi, dikonfigurasi liwat konstruktor — supaya bisa nglambungake data lan prilaku karo saben tetapan. Iki unika lan kuwat tinimbang enum basa liya.

## Enum bisa ngleksanani antarmuka lan duwe tingkah laku saben-tetapan

```java
public enum Operation {
    PLUS { public int apply(int a, int b) { return a + b; } },
    TIMES { public int apply(int a, int b) { return a * b; } };
    public abstract int apply(int a, int b);   // each constant implements it differently
}
Operation.PLUS.apply(2, 3);   // 5
```

## Enum yaiku singleton sing luwih apik

```java
public enum Config { INSTANCE; /* fields/methods */ }
// enum singletons are thread-safe and serialization-safe by design
```

## Mengapa iki penting

Enum Java yaiku cara sing kuat lan aman tipe kanggo nampilake tetapan sing wis ditétepake (kaanan, dina, peran, operasi) — luwih apik tinimbang alternatif sing mudah salah yaiku tetapan `int`/`String`, sing ngidini nilai ora sah lan ora menehi pariksa tipe.

Kuwate unika — medan, konstruktor, metode, pelaksanaan antarmuka, lan tingkah laku saben-tetapan — ngidini sampeyan nglambungake data lan logika ing saben tetapan, mula bisa modél konsep domain kanthi graceful (contone planet karo massa/gravitasi, operasi karo matematika-e).

Kabehan uga nyediyake idiom singleton sing paling aman.

Nemahi enum utawa luwih saka daftar tetapan prasaja — minangka kelas lengkap karo kaanan lan tingkah laku — nyegaake modél domain sing luwih resik lan aman, uga fitur Java sing jarang digunakake nanging berharga, lan topik wawancara sing sering.