libaddressinput
The libaddressinput project consists of two different libraries (one implemented in C++, one implemented in Java for Android) that use address metadata from Google's I18n Services Address Data Service to assist application developers in collecting and handling postal addresses from all over the world.
These libraries can provide information about what input fields are required for a correct address input form for any country in the world and can validate an address to highlight input errors like missing required fields or invalid values.
The C++ library (in very portable C++03) of libaddressinput is the backend for requestAutocomplete() in Chromium. The source code for that is a good example of how to use this library to implement a complex feature in a real application:
https://src.chromium.org/viewvc/chrome/trunk/src/third_party/libaddressinput/ https://chromium.googlesource.com/chromium/src/+/master/third_party/libaddressinput/
Video: Easy International Checkout with Chrome
The Java library of libaddressinput is written for use in Android and includes an Android UI address input widget ready for use, but only the UI parts are tied to Android (all the non-UI unit tests can be readily run in Java SE, ant junit) and the rest of the library could easily be adapted to run in any Java environment.
Using and developing libaddressinput is discussed on this mailing list:
https://groups.google.com/forum/#!forum/libaddressinput-discuss