现在在特定小时的Java 8 LocalDateTime(Java 8 LocalDateTime today at specific hour)

 所以，怯懦地回答我自己的问题...... 
 
 我找不到用Class<?>做的任何方法，但是这种称为超级类型令牌的神奇技术似乎运作良好。 以下是更新的代码： 
 
public class Test {

    static class A {}
    static class B extends A {}


    public static void main(String[] args) throws Exception {
        Holder<HashSet<Integer>> i = newObjectHolder(new TypeReference<HashSet<Integer>>() {});  // works
        Holder<A> j = newObjectHolder(new TypeReference<A>() {});  // works
        Holder<A> k = newObjectHolder(new TypeReference<B>() {});  // works
        Holder<B> l = newObjectHolder(new TypeReference<A>() {});  // doesn't compile (good)
    }

    static class Holder<T> {
        public Holder(T newInstance) {}
        T get() { return null; }
    }

    public static <T,U extends TypeReference<? extends T>> Holder<T> newObjectHolder(U typeToken) throws Exception {
        T obj = typeToken.newInstance();
        return new Holder<T>(obj);
    }
}
 
 这里给出了 TypeReference代码，尽管我怀疑Guice的TypeLiteral会起作用（但它没有newInstance代码，你必须实现它）。 

So, sheepishly, answering my own question...
 
I can't find any way to do it with Class<?>, but this magic technique called super type tokens seems to work well. Here's the updated code:
 
public class Test {

    static class A {}
    static class B extends A {}


    public static void main(String[] args) throws Exception {
        Holder<HashSet<Integer>> i = newObjectHolder(new TypeReference<HashSet<Integer>>() {});  // works
        Holder<A> j = newObjectHolder(new TypeReference<A>() {});  // works
        Holder<A> k = newObjectHolder(new TypeReference<B>() {});  // works
        Holder<B> l = newObjectHolder(new TypeReference<A>() {});  // doesn't compile (good)
    }

    static class Holder<T> {
        public Holder(T newInstance) {}
        T get() { return null; }
    }

    public static <T,U extends TypeReference<? extends T>> Holder<T> newObjectHolder(U typeToken) throws Exception {
        T obj = typeToken.newInstance();
        return new Holder<T>(obj);
    }
}
 
The TypeReference code is given here, although I suspect that Guice's TypeLiteral would work just as well (but it doesn't have newInstance code, you'd have to implement it).