Find Java classes implementing an interface [duplicate]

Answer 1

Package Level Annotations

I know this question has already been answered a long time ago but another solution to this problem is to use Package Level Annotations.

While its pretty hard to go find all the classes in the JVM its actually pretty easy to browse the package hierarchy.

Package[] ps = Package.getPackages();
for (Package p : ps) {
  MyAno a = p.getAnnotation(MyAno.class)
  // Recursively descend
}

Then just make your annotation have an argument of an array of Class. Then in your package-info.java for a particular package put the MyAno.

I'll add more details (code) if people are interested but most probably get the idea.

MetaInf Service Loader

To add to @erickson answer you can also use the service loader approach. Kohsuke has an awesome way of generating the the required META-INF stuff you need for the service loader approach:

http://weblogs.java.net/blog/kohsuke/archive/2009/03/my_project_of_t.html