Considering that the Samurai class had its distant roots in Chinese political structure, did China or Korea have a similar warrior class?
In China, there were warriors similar to ronin - the xia. As a link, I found only those regarding their philosophy or literature about them. GURPS Martial Arts (it's no solid historical work and I didn't manage to find any better source) states they were more like Robin Hood than Lancelot - they were not upper class like samurai.
Korean Hwarang are approximation of Samurai from the other side - they were upper class young men probably serving as warriors, but it's not their defining feature. In GURPS Martial Arts they are presented as very similar to Samurai, but when I consider what is written in Wikipedia, it might be just a myth.
There is a Chinese saying (in pinyin), "Hao tie bu da ding, hao ren bu dang bing." (Good iron is not used to make nails. Good men do not become soldiers.)
For most of Chinese history, soldiers were vilified, rather than honored. Hence, they would not generally be regarded as members of the upper class, which was occupied by landowners and philosophers.
Most of Korea, whose culture is more similar to China's than Japan's felt much the same way.
Before China was unified there was a warrior class(mostly noblemen), until the warlords realized that they could hire peasants with a cheap price and give them cheap weapons to expand their army. After that, most noblemen became scholars or military commanders, because of the change in the tactics of warfare(the ceasing of chariot warfare and agreed warfare,and the start of surprise attack which were considered treacherous by the noble warrior class but was promoted by Sun Tzu and so on.)
Korea had a Yangban class which might be compared with samurai status but was closer to the Chinese scholarly ruling class. Most historians hold that the scholar class achieved power in China (or Chinese dynasties of whatever race, except perhaps the Mongol Yuan one) while the warrior class gained power in Japan. During the late 17th, 18th and early 19th centuries, this warrior class became a scholarly administrative class, or at the lower level a parasite class who lived off peasants' labour through small stipends from their clan lords. A few clans, notably, Satsuma, allowed samurai to also engage in horticulture, but they were the exception rather than the rule.
In Korea (gojoseon goguryeo baekje shila Balhae goryeo joseon etc) you were either commoner, slave, yangban (rich gentlemen class?), scholar, or a warrior called Muin or Musa. 2 of the ways of getting a government position were to become a scholar or a muin thru tests.
A warrior class like the ninja came about because commoners wanted to fight upper class. There wasn't really a situation like this in Korea. Those who wanted to fight became musa and just killed or simply payed back. But there was "Gaema Budae", "Gemma Squad" or Chulgap busae. These were squads of warriors who were fully armored in the strongest metal armor and even their horses were fully armored.
Chulgap was made with small plates of metal about inch x 2 inch large that were stitched together like fish scales. This made the armor lot more flexible unlike plate armors used by rest of the world, it was very light like leather but stronger than plate armors. Armors made with plates like used in china and rest of the world can be pierced by strong Metal tip arrow but chulgap was nearly impossible. All goguryeo armors were made in fish scale style. Later other parts of world did the same.
Studies found out Korea was first to use this style of advanced armors which were one of lightest and strongest. Also their shoes were embedded with spikes on the bottom to kick and stab enemies who were too close while fighting on horse. This was also found to be first invented in Korea. Yes there were other armies who were fully armored head to toe in other parts of world but not like goguryeo. Also GGR was one of if not the first to fully armor their horses since the bc times.
There were monks who learned to fight (like Shaolin) but studied secret Korean martial arts strictly for quickest killing silent as possible. They had the simplest armor that only covered the most vital area to increase their speed. One way their were called were JoEuiSunIn. When country was in trouble they worked as mercenaries. They weren't part of any body of government nor any army but them selves. They would sneak into enemy territories and burn their supplies and murder the leaders.
In Korea warrior classes were more separated by style of martial arts they studied than creating whole new class like Japan. There were many more martial arts in Korea than just tae kwon do hapkido taekyun etc.
Not a myth, a fact. For 1800 years in the Silla kingdom, aka Slusa, they pre-date samurai. By the examples I've seen in writings, their armor looks as if the samurai copied them. In fact, they have code of 5 rules of conduct governing them from Buddhist and historical archives.
The Qing Dynasty were not truly "Han" so while I would not call them Samurai in the sense of a "way of being" to say they weren't militaristic would be an understatement. You would have to do your research on this matter to devise your own conclusions. The only thing I recall is that the "Manchu's" had a highly advanced form of communication that allowed them to move truly massive Armies over great distances. They weren't considered to be "warrior like" upon ruling the entirety of what we would call Modern China today...but I believe besides being the last Dynasty they also ruled the longest.
of course for example, jinyiwei or dongchang,secret polices of Ming. everything you see from Japan or Korea were from China, ninja is just Japanese version of China Wuxing Taoists.