@Override
                protected Field<T> copy(IdStrategy strategy)
                {
                    return POLYMORPHIC_POJO.create(number, name, f, strategy);
                }
Field factory via sun.misc.Unsafe.

@author David Yu
@created Jul 7, 2011
protostuff-runtime/src/main/java/io/protostuff/runtime/RuntimeUnsafeFieldFactory.java