The Japanese economy was strong and stable in 1980, despite the strains of a new oil price increase, and most experts look for a performance just as good or better next year.

An exceptionally strong export performance kept the wheels turning this year. Economists hope that next year's gains will rely proportionally more on domestic consumption.

Compared to other industrial countries, Japan's economy keeps churning along at an enviable pace, turning in respectable growth rates with modest inflation and a low unemployment rate.

Heading into the current fiscal year, which began last April 1, the Economic Planning Agency predicted an annual growth rate of 4.8 percent in real terms. The EPA now believes it will meet the target and gross national product will have grown by 4.7 percent when the fiscal year ends next March.

The outlook for fiscal year 1981 varies slightly among government planners and those who work for economic research companies.

Government planners are the most optimistic, and they plan on a 5.3 percent growth rate next year. One of the leading private organizations, Nomura Research Institute, is slightly less optimistic, putting it at only 4.1 percent.

An unexpectedly strong surge in exports of automobiles, steel and other products led the Japanese economic advance this year and made the charts look good even as they were arousing hostility in the United States and Europe.

Overall, exports will increase 18.4 percent in the current fiscal year, compared to the last one. It was far above expectations. Planners had expected an increase of only 8.9 percent.

Automobile exports soared almost 30 percent this year, raising howls of anger and legal assaults in the U.S. and Europe. During much of 1980, Japanese car makers ignored appeals of their own government to slow down their exports in the interest of allied harmony.

The steel industry increased exports by about 10 percent and electronics sales overseas also did well. Japan's overseas sales of video tape recording devices were 80 percent greater than last year.

Exports may not play such an important locomotive role in the coming year, however, due to political and currency pressures.For one thing, criticisms from abroad of Japan's export binge are hitting home, and some experts think the high point is past.

"We have already reached the peak," said Toshiaki Kamijo, managing director of Nomura Research Institute. "If we push for more, the antagonism against Japan will only increase."

A second barrier blocking a continued export surge, economists believe, is the future of the yen. There is a general belief that the yen will appreciate considerably in the coming months, making Japan's exports more expensive and ultimately slowing the pace.

Some experts see the yen rising to a level of 190 to the dollar on the average during the fiscal year that begins April 1. In late December, it was hovering around the 210-per-dollar mark.