Java is a relatively new programming language that is gaining popularity due to its network-centric features and platform independence (Write Once, Run Anywhere). This popularity has caused rapid evolution in the libraries that are available for Java applications. This evolution, in combination with Java's run-time linking, may cause incompatibilities between an application and the library it depends on: an application may execute with a different library version than the one it was compiled for. This paper presents techniques to automatically detect change in a library from its bytecode (binary) representation, and to apply the impact of those changes to any Java application. This paper also includes results of change detection experiments performed on the standard Java library (JDK).