Generics ngidini sampeyan nulis kelas, interface, lan metode sing manggon karo type parameter sing dierangne dening manggel — nyedhiyake type safety saka jam kompilasi lan ngilangi casting. Lan nguwehi daya Collections Framework lan perpustakaan sing bisa dibalekake.
();
list.add();
list.add();
(String) list.get();
List<String> list = <>();
list.add();
list.add();
list.get();
Generics mindhah kesalahan tipe saka runtime (ClassCastException) dadi compile time, lan ilang kebutuhan casting manual — bisikin kode luwih aman lan resik.
// 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> ngebateske type parameter, ngidini sampeyan nganggo anggota tipe kasebut kanthi aman.
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 nambah fleksibilitas kanggo parameter metode sing kudu trima jangkauan tipe.
// 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 nglakokake generics liwat type erasure — type parameter ana ing kompilasi nanging dihapus ing runtime, sing nduweni sawetara batasan.
Generics penting kanggo Java modern — nyedhiyake type safety ing compile time (narap kesalahan tipe paling awal tinimbang minangka runtime ClassCastException), ngilangi casting sing verbose lan rawan kesalahan, lan ngidini kode sing bisa dibalekake lan type-flexible.
Lan dhasar saka Collections Framework kabeh (List<String>, Map<K,V>) lan perpustakaan sing ora katara.
Paham generik kelas/metode, parameter kebatasan, wildcard (PECS), lan ngati-ngati type-erasure ngidini sampeyan nganggo API generik kanthi bener lan nggawe abstraksi sampeyan dhewe sing bisa dibalekake lan aman tipe — katrampilan inti kanggo nulis Java sing kuat lan bisa dirawat.
Pustaka pitakon wawancara IT kanthi jawaban rinci — saka Junior nganti Senior.
Nyumbang