I don't know why people keep comparing China to Japan, the only real similarity is that they're both in east Asia. China has an order of magnitude more people, isn't a small island, has a larger military, different form of government, different economic system, etc. etc.
Much of China's debt is in the form of housing and infrastructure - it's debt nonetheless, but is also an asset. Not all debt is strictly a "liability." Not to mention Chinese citizens save far more than American's, so a simple comparison of the total debt load isn't entirely fair to either nation.
China's main issue is not making sure their (debt) investments are fueling more growth and not going into the ether, like other countries' debt. Of course, this challenge is hardly unique to China. Fortunately for them, they have a large domestic population to use to fuel growth. They'll just need to make sure they can properly incentivize more population growth to keep the positive feedback loop humming along.