java - Generics and Class, deciding subclass in constructor -

i want able have (one of) constructor decide implementation of list wants use. code came compiles fine without warnings ide (eclipse) complains on commented line, why , how infer type?

public class genericclasstest<t> {  private list<t> list;  //stuff...  public genericclasstest(class<? extends list> listcreator)         throws instantiationexception, illegalaccessexception {     this.list = listcreator.newinstance(); // how infer type t?                                             // diamondoperator go? }  public static void main(string[] args) throws instantiationexception,         illegalaccessexception {     genericclasstest<integer> 1 = new genericclasstest<>(arraylist.class);     genericclasstest<string> 2 = new genericclasstest<>(linkedlist.class);     one.list.add(13);     two.list.add("hello");     system.out.println(one.list);     system.out.println(two.list); }   } 

you don't need to. remember type-erasure going replace t object @ runtime anyway. @ runtime have list<object>. therefore, doesn't matter if t part of construction call since ignored anyway. generics compile-time convenience, not lot @ runtime.