Borrowing and Saving

David Frum points out that Germany has benefited greatly by having the Eurozone, locking in the periphery as customers, who borrowed from the Germans:

By folding all of Europe's currencies into the euro, Germany prevented its neighbors from reducing their costs — thus enhancing German exports and preserving German jobs.
In the decade from 2000 to 2010, Germany's share of world trade rose by almost 9 percent (most of that being exports to other European countries).
The same currency that made German exports more competitive also made the exports of other European countries less competitive. Their shares of world trade declined over that same decade — in France's case, by a spectacular 23 percent.
But the less competitive countries did get something out of the euro: Lower interest rates. The currency arrangement that enabled Germany to sell more enabled Greece, Italy, Spain, and France to borrow more.
Germany got the jobs. Greece and the others got the debts.

It is much the same in China.  For a country to run a trade surplus, they have to provide credit to their customers.  If you keep providing the customers with credit, they eventually won't be able to pay it back.  If you cut off the credit, your economy will tank.  It's a trap, and both nations are in it.