In September 2017, the J-20 officially entered military service with PLAAF, making China the second country in the world after United States wielding fifth-generation stealth aircraft, and the first in Asia.[87][87][88][16]
In January 2018, Chinese media reports that J-20 is in full operation-ready deployment.'
Yeah, that all sounds great as propaganda. It's clear to any knowledgeable observer that the J-20 likely still has significant issues. As I mentioned before, it's also not at all clear how stealthy it is as well. There's a reason no other stealth aircraft has canards...
"in two years’ time, if not before, America is likely to lose its monopoly of radar-beating stealth combat aircraft with the introduction into service of China’s Chengdu J-20. This has a much longer range than America’s new F-35 fighter and will be a serious threat to American warships in the Pacific."
Carrier based F-35s will be in service soon (or already are in the case of the F-35B), countering the range advantage. All that said, the F-22 is the true counterpart to the J-20 and will likely mop the floor with it if necessary.
It's worth noting that for strike aircraft like the F-35, the main goal is avoiding detection to bomb targets. Stealth aircraft have no advantage over any other aircraft at detecting other stealth aircraft - making the J-20 no more of a threat than any Gen 4 aircraft.
"Another system, yet to be named, would provide China with an ability to knock out targets as far away as 400km, a far greater range than any other air-to-air weapon in service. It would threaten aircraft that currently operate safely from a considerable distance, such as tankers and planes used for airborne surveillance and control. "
Yep, that's interesting. I wonder how our jammers, anti-missile missiles, and directed energy weapons will fare against it...