Java generics: capture generic type when copying instances of subclasses -

in following code sample, there way avoid ugly suppresswarnings annotations?

the code tests if parameter t instance of a , returns instance of a if so. satisfies general contract of createcopy() return object of same type parameter, safe operation. same goes test b.

i know wildcard capture , helper methods i'm not sure if , how helps in situation although problem appears quite similar.

abstract class base {     public static <t extends base> t createcopy(t t) {         if (t instanceof a) {             @suppresswarnings("unchecked")             t copy = (t) new a((a) t);             return copy;         }          if (t instanceof b) {             @suppresswarnings("unchecked")             t copy = (t) new b((b) t);             return copy;         }          throw new illegalstateexception();     } }  class extends base {     public a() { }     public a(a a) { } }  class b extends base {     public b() { }     public b(b b) { } } 

you can pass class method, that's still ugly:

abstract class base {     public static <t extends base> t createcopy(final t t,             final class<t> klass) {         if (t instanceof a) {             final t copy = klass.cast(new a((a) t));             return copy;         }          if (t instanceof b) {             final t copy = klass.cast(new b((b) t));             return copy;         }          throw new illegalstateexception();     } }  class extends base {     public a() {     }      public a(final a) {     } }  class b extends base {     public b() {     }      public b(final b b) {     } } 

calling t.getclass() doesn't work either. reason t can subtype of or b (that's why code not type-safe).

edit : why code not type-safe: imagine class aa extends a. if call method instance of class, create object of type a , try cast aa.