Re: newInstance, generics, and "unchecked or unsafe operations"

Stanimir Stamenkov <>
Fri, 15 Aug 2008 15:38:27 +0300
Fri, 15 Aug 2008 00:08:17 -0700, /Eric I./:

I'm trying to create a method in a class that takes some type of
genericized collection and creates a new, empty instance of it by
calling the newInstance method. I can get the code to work, but I do
get compiler warnings of "unchecked or unsafe operations".


class EmptyDuplicator<T>
    public Collection<T> duplicateEmptyVersionOf(Collection<T>
           throws InstantiationException, IllegalAccessException
        // COMPILER WARNING on next line; BUT I KNOW T at compile-
        Collection<T> emptyVersionOf =
        return emptyVersionOf;

Recently one has mentioned the Class.asSubclass [1] method but I
can't figure out which is the correct syntax, or if it is possible
at all:

         Class<? extends Collection<T>> c;
         // Syntax error in the |Collection<T>.class| part.
         c = original.getClass().asSubclass(Collection<T>.class);
         Collection<T> emptyVersionOf = c.newInstance();



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