Where can I find a reasonably complete Java example for connecting to ExactTarget and updating a Data Extension.
It isn't in the documention. I've looked there already. ET just says its coming. Does anyone have simple examples they can share?
These examples are available starting here. There are specific code snippets available for most common use cases.
This has Java code snippets available for all commonly used entities.
You can look into the Fuel Java SDK test folder https://github.com/salesforce-marketingcloud/FuelSDK-Java/tree/master/src/test/java/com/exacttarget/fuelsdk. Seems pretty good to me.
You can looking on unit-test of Fuel-SDK. This should help you start.
If you are looking using Proxy with Fuel SDK then check out https://github.com/nidongara/FlamesSDK-Java