''Friendship and knowledge,'' Hu Yaobang says, are the twin purposes of his visit to Japan Nov. 23 to 30. A taxing itinerary for the general secretary of the Chinese Communist Party shows that he was not just being polite when he made this comment to a group of Japanese journalists visiting Peking.
Diplomatic observers believe it to be significant that Mr. Hu has chosen Japan as the first capitalist, Westernized democracy he is to visit.
Whereas President Reagan spent just two days in Japan, Mr. Hu is taking eight days to explore the country from Hokkaido in the north to Nagasaki in the south. He will be received by Emperor Hirohito, will talk international and bilateral issues with Prime Minister Yasuhiro Nakasone, and discuss Sino-Japanese relations with a representative group of Japanese young people.
He will see a village opened by Japanese settlers in Hokkaido in the last century as well as the latest explorations in electronics being conducted by government laboratories in Tsukuba, Japan's science city. He will inspect a Matsushita television line in Osaka and Mitsubishi's giant shipyard in Nagasaki. He will tour Kobe's man-made port island and Kyoto's feudal Nijo castle.
Whether all this will be sufficient to give China's diminutive Communist Party leader an accurate impression of what makes Japan function remains to be seen. But observers here and in Peking believe Mr. Hu is genuinely interested in understand Japan and why it has been so successful in its economic modernization.
He seems equally sincere when he notes that Japan and China, though neighbors for centuries, have been really friendly for only the past 11 years, since the signing of the Sino-Japanese treaty of peace and friendship, that this newfound friendship must be handed down to the next generation, and that he intends to make a lifetime commitment to this cause.
Neither Mr. Hu nor his hosts can forget that during much of the past century Japan followed the example of Western colonialist powers in invading China and gaining territory and economic privileges. But Mr. Hu has also told visitors that he was impressed by the late Prime Minister Shigeru Yoshida's memoir of Japan's 100-year struggle to modernize its economy and to catch up with the industrialized West.
In ideological terms, Mr. Hu is a committed Communist, a longtime activist in the Communist Youth League and a follower of senior leader Deng Xiaoping.
He is, at the same time, a pragmatist, like Mr. Deng himself, searching for ways in which China can apply the achievements of Western science and technology to its own very different conditions. He would even be interested in seeing what aspects of Western institutions could be adapted to China's circumstances.
In this sense, Mr. Hu comes to Japan like an explorer seeking usable ideas. The way in which Japan, a Confucian country, adapted Western institutions while retaining its own cultural identity will surely be of interest to Mr. Hu.
Of course Japan has but one-tenth the population of China. Can a system that works for a tight, little island society like Japan be adapted to huge, continental China where all kinds of conflict have been endemic for centuries? The Japanese themselves do not seem very confident on this point. There is no missionary zeal to export Japanese institutions.
Some Japanese are uneasy over prospects for China's stability and prosperity. Peking's current drive against mental pollution, and the Draconian punishments meted to young hooligans and other criminals have also caused concern in Tokyo.
Is Peking's leadership turning the clock back to a period of more rigid social, political, and ideological control? Is such control compatible with the open door Peking insists it will maintain toward economic cooperation with industrialized countries, including Japan?
As the people of Japan, moving out of feudalism into an almost classless society, found that they could not modernize without wrenching social, political , and economic changes, so the China may discover that if its modernization is to succeed, it will have to include much more than material changes - it will have to encompass the mental realm as well.