Generics nglempimu nulis klas lan metode sing parameterized dening tipe, supaya kodhe sing padha bisa ana ing pirang-pirang tipe ning tetep keamanan tipe ing wektu kompilasi. Iki dadi polimorfisme parametrik — "siji wujud, saben tipe".
();
list.add();
(String) list.get();
// With generics: type is known and checked at compile time
List<String> list = new ArrayList<>();
list.add("hi");
String s = list.get(0); // no cast; list.add(42) won't compile
class Box<T> { // T is a type parameter
private T value;
Box(T value) { this.value = value; }
T get() { return value; }
}
Box<Integer> b = new Box<>(42); // T = Integer, checked at compile time
int n = b.get(); // no cast needed
<T extends Comparable<T>> // bounded: T must be comparable
List<? extends Number> // covariance: accept List<Integer>, List<Double>
Java ngilangi jenis generik ing runtime (type erasure) — sampeyan ora bisa nglakoni new T() utawa instanceof List<String>. Template C++ lan generics C# kelakuan beda (monomorphization / reified types).
Generics menerangake panggunane lan keamanan bebarengan: siji List<T> nggarap saben tipe elemen, lan kompiler nangkep kesalahan tipe sing ateges bakal kacilakan runtime.
Semina ngilangi cast sing ora aman lan dadi atasan koleksyon, nggawa kode luwih bisa digunakake maneh lan luwih angel salah pakey.