The line of blue-plastic huts along the banks of the Sumida River, built by the homeless here whose numbers have nearly doubled in four years, is one sign of Japan's painful economic restructuring.

The human side of this upheaval in the Japanese workplace also is evident in the soaring suicide rate, in the new corps of jobless who spend their days on park benches so their families think they work, and in the despair of new graduates collecting rejection slips.

Japan is perhaps uniquely ill-suited for the wrenching dislocation that other economies have experienced, including the "downsizing" of America's industrial base. The nation's post-World War II boom was built on an ideal of loyalty to one company, rewarded by lifetime employment.

Now middle-aged men are thrust out of work in a culture where changing jobs is difficult, where unemployment still carries a stigma, where age discrimination is legal, and there is little social safety net.

The country was shocked last March when one distressed longtime employee of the tire manufacturer Bridgestone Corp. committed suicide after holding his company president hostage. That was the most public of what were nearly 33,000 suicides, by far the highest number since World War II, and three times the number of automobile fatalities.

Police, who keep careful track of this phenomenon, said the largest increase was in suicides caused by economic worries, including job loss and forced early retirement.

Nobuhito Kimiwada, who helps run a legal help-line for distraught workers, said: "We talk about restructuring, but we ought to have a goal. One goal is to get more profit for stockholders. In the American system, there is a huge discrepancy between the rich and non-rich, at the expense of the workers. Is that what our goal should be? I seriously hope not."

Japan's unemployment rate has been on a decade-long upward march. At 4.5 percent it seems low by American standards, but in Japan it is only a notch below last summer's 4.9 percent historic high. The unemployment rate among men 24 or younger is officially 10.7 percent, but analysts say it is likely much higher.

The jobless also include many middle-aged men who will be unable to find jobs matching their skills or former salary. These are casualties of company cutbacks, such as the 51,000 Nissan Motor Co., Nippon Telephone & Telegraph Corp. Mitsubishi Corp. announced recently.

"People are not fired--it's not American-style layoffs," said Akira Takanashi, chairman of the government-sponsored Japan Institute of Labor. Instead, more than half of large companies have "early retirement" programs that encourage--or, in any cases, force--employees to quit as early as age 49.

Those who do not take the hint can be treated heartlessly. Stories abound of employees shunned, with no work, no responsibility and no real contact with the other employees until they quit.

Those who leave usually get a buyout bonus and unemployment compensation, but can find themselves out of money before finding an equivalent job. Kazuo Kondo, 51, lost his job in apparel sales after his company went bankrupt a year ago. Each week he makes the rounds of three big employment agencies, but all he sees posted are cleaning and security jobs. "I'd like to find something in a similar field so I could use my experience," he said.

The government is beginning to pour money into job training, spending $4.5 billion on programs it says will create 700,000 jobs. Akira Taguchi, 55, hopes to get one of them. He had no computer skills when he was laid off last April. Now he is taking an Excel '97 class at a technical college. "After I finish the course, I'll go and see as many companies as possible," he said cheerfully.

If he succeeds, he will be an exception. Age discrimination is legal here; many job ads are grouped according to age. Companies still steeped in the custom of recruiting a worker for life are more inclined to hire a new graduate than an experienced employee.

But that traditional route is increasingly fruitless. Tokyo's Nihon University used to send 40 percent of its graduates to Japan's biggest companies. Now it sends 5 percent to 7 percent.

Former construction worker Sadao Kaneko, 54, moved with his wife into a plastic-draped shelter they built by the riverside after his last two employers went bankrupt. Kaneko and his wife, Kazuki, have a candle for light, they cook on a camping stove and venture out during the day to look for odd jobs. They rarely succeed. "I'm pretty discouraged," he said.

Higher on the embankment, Isao Takeda sleeps on a cardboard mat on the ground. He lost his job and his dormitory quarters when the public bath where he worked for six years closed. "My parents think I still work," he said, adding that at 56, "it's very difficult for someone my age to find a job."

Special correspondents Akiko Kashiwagi and Shigehiko Togo contributed to this report.

CAPTION: Huts covered in plastic have sprung up along the Sumida River, where the homeless have set up camp. Japan's current jobless rate of 4.5 percent, though low by U.S. standards, is only down slightly from the historic high of 4.9 percent.