His confidence stems from the availability of the aircraft.

Currently, there are more than 100 F-22's in service.  The US congress has set the F-22 production number as 187 in 2009, while J-20 is just entering test flight stage. 

It is not surprising that he is more worrying about a weapon, namely DF-21D, that presents a real threat to his troops at this moment. 

I think that he will retire from servie in 10 years.  It is another reason why he pays less attention to J-20.