A constructor tansah nggawe instance anyar saka klasé sing tepat, kanthi jeneng tetep marang kelas. A factory method yaiku metode reguler (asring static) sing nggawe obyek — menehi sampeyan kebebasan babagan jeneng, subtype apa sing bakal dikembalake, lan apa sampeyan kudu nggawe obyek anyar utawa ora.
public class Color {
private final int r, g, b;
private Color(int r, int g, int b) { this.r=r; this.g=g; this.b=b; }
// Named factories: clearer intent than overloaded constructors
public static Color fromRgb(int r, int g, int b) { return new Color(r,g,b); }
public static Color fromHex(String hex) { /* parse */ return new Color(0,0,0); }
// Can return a CACHED instance instead of always allocating
private static final Color BLACK = new Color(0,0,0);
public static Color black() { return BLACK; } // no 'new' every call
}
| Constructor | Factory method | |
|---|---|---|
| Jeneng | Tetep marang kelas | Deskriptif (fromHex) |
| Jinis bali | Persis kelas iki | Subtype / interface apa wae |
| Identitas | Tansah anyar | Bisa cache/pool/reuse |
| Bisa gagal kanthi lempem | Throw | Bisa bali null/Optional |
Optional<User> u = User.tryParse(json); // a constructor can't return Optional
Factory nambah indirection lan bisa ndhelikake apa sing bener-bener dikonstruksi. Gunaake constructor wadon kanggo pembuatan nilai sing simpel; gunakake factory nalika sampeyan butuh jeneng, bali polimorfik, utawa kontrol instansi.
Factory method nglokalisir pemanggil saka kelas konkret — sampeyan bisa nggawe instance beda utawa instance cache tanpa ngganti situs panggilan.
Ugene nggawe API luwih jelas: Color.fromHex("#fff") maca luwih apik tinimbang overload constructor, lan factory jeneng ngatasi ambiguitas multiple konstruktor sing padha-padha tipe.