How exactly? You can still -target 1.4 and there hasn't been any removed APIs.

Incompatible changes:

  - Ongoing changes to method selection within major and minor releases
  - Various breakages when generics where introduced
  - Various breakages when Swing was generified in Java 5, 7 and 9
  - Change of visibility or removal of methods caused by security issues
  - Deprecation and upcoming removal of various methods due to modularization plans