Untitled

How do I build a Java type object at runtime from a generic type definition and runtime type parameters?
class Foo<T> {
    public T bar;
}

class Foo<T> {

    Class<T> clazz;

    public Foo(Class<T> c) {
        clazz = c;
    }

    public T bar {
        return clazz.newInstance();
    }
}

public class JsonWrapper {
    private String className;
    private String json; // the output of the gson.toJson() method
}