An enum yana bayyana nau'i mai ɓangare na ɓare na su'ami masu suna. Enums Java sun fi ɗan ƙarfi masu sauƙi na madaidaita a harsuna daban — kuma jami'u ne masu cikakken karfi waɗanda za su iya samun filayen, masu gina gida, da hanyoyi.
{
MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY, SUNDAY
}
Day.MONDAY;
(today) {
MONDAY -> System.out.println();
SATURDAY, SUNDAY -> System.out.println();
-> System.out.println();
}
Enums suna ba da sauri cewa jiya — Day today = Day.MONDAY zai iya ajiye kawai m akai Day, ba kamar amfani da saiti ko jeri kadir saboda su'ami (wanda ya ba da damar ba asali akai da su'almai).
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
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
Kowanne enum ƙauna shine nau'i, wanda aka shimfiɗa ta hanyar masu gina gida — ba ka mai ɗaukar bayanan da hali ga kowa ƙauna. Wannan ya kasance kaɗai da karfin idan aka kwatanta da enums na gida yawancin harsuna.
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
public enum Config { INSTANCE; /* fields/methods */ }
// enum singletons are thread-safe and serialization-safe by design
Enums Java su ne abin lafiya, cikakke-amfani hanya don wakilta ɓangare na su'ami masu alaƙa (jiƴi, ranar, jika, aiki) — da fa kamayen gida na integers/strings su'ami, wanda ba asali akai da sallama ba da gyaran nau'i.
Su dalilin karfi — filayen, masu gina gida, hanyoyi, aiwatar interfaces, da ɗaya-ɗaya hali — ba ka mai ɗaukar bayanan da tunani ga kowa ƙauna, ƙira jiya ma'auni ga kira (misali jiƴi tare da nauyi/graviton, aiki tare da ilimin su).
Su kuma ba da mafi sauri singleton.
Dimewa enums fiye da sauƙi su'ami jami — kamar cikakke jami'u tare da jiƴi da hali — ba ka mai shida, kalinawa jiya ga duka, ba ja hanya Java karfi, kamar kuma kaida jiya labari.