Generics yana ba ka damar rubuta azuzuzukoki, interfaces, da hanyoyin aiki tare da sigar sigar da wanda aka saba — sanin aminci iri a lokacin lokaci da kuma kawar da jankaka. Suna ba da wuri ga Collections Framework da maimaitawa da maimaitawa.
();
list.add();
list.add();
(String) list.get();
List<String> list = <>();
list.add();
list.add();
list.get();
Generics suna motsa kuskuren iri daga runtime (ClassCastException) zuwa lokacin harrashi, kuma sune kawar bukatun janci kai - sanya kodda akwai aminci sosai da kuma sauki.
// a generic class — T is a type parameter filled in by the user
public class Box<T> {
private T value;
public void set(T value) { this.value = value; }
public T get() { return value; }
}
Box<String> b = new Box<>(); // T = String
b.set("hi");
String x = b.get(); // typed, no cast
// a generic method
public static <T> T firstElement(List<T> list) {
return list.get(0);
}
// T must be Number (or a subclass) — lets you call Number methods
public static <T extends Number> double sum(List<T> list) {
double total = 0;
for (T n : list) total += n.doubleValue(); // safe — T is a Number
return total;
}
<T extends X> ya iyakance sigar sigar, yana ba ka damar amfani dashi nan gida.
List<? extends Number> nums; // "some subtype of Number" — read (producer)
List<? super Integer> sink; // "Integer or a supertype" — write (consumer)
// PECS: Producer Extends, Consumer Super
Wildcard yana ba da sauyi ga sigar sigar da yakamata su yarda da kewayon nau'i.
// generics are a COMPILE-TIME feature — erased at runtime (for backward compatibility)
List<String> a = new ArrayList<>();
List<Integer> b = new ArrayList<>();
a.getClass() == b.getClass(); // true — both are just ArrayList at runtime
// consequence: can't do `new T()` or `instanceof List<String>`
Java yana aiwatar da generics ta hanyar nishewa nau'i — sigar sigar yana kasancewa a lokacin harrashi amma ana cire su a lokacin aiki, wanda ke da iyakance.
Generics mahimmanci ne don Java zamani — suna ba aminci iri a lokacin harrashi (sami kuskuren iri da sauri a maimakon ClassCastException a lokacin aiki), kawar da jance da kuskuri, da ba da damar maimaitawa, aminci-jiya kodda.
Su ne tushe na duka Collections Framework (List<String>, Map<K,V>) da kasua.
Nisantar ajin/hanyoyin generics, sharudduka an iyakance, wildcard (PECS), da ganye nishewa nau'i yana ba ka damar aiwatar da aminci-iri API da kyau da kuma ƙera niki nisu maimaita da aminci-aminci - mahimman sana'a don rubuta Java ƙarfi, jiyya.