How to look for wrappers (decorators) of specific classes?

Question

I had a job interview recently and I was supposed to do an exercise where one part of the coding was using the ExecutorCompletionService. Well, there were other ways, but this would have been the easiest.

My problem : I did not know about this. After I found out about this, I could look it up easily (tutorials, examples, documentation, even source code)

Could I have found this wrapper using online resources only? (I mean if I download the source code of the JDK, I can used a normal IDE to look for usages of classes, but can I do this online?)

Answer 1

First of all you can use the Javadoc provided by Oracle: https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/ExecutorCompletionService.html

If a class or interface has known (= part of the JDK) subclasses or implementing classes, they will be listed at the top.

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Another online service I use sometimes is GrepCode: http://grepcode.com/file/repository.grepcode.com/java/root/jdk/openjdk/8u40-b25/java/util/concurrent/ExecutorCompletionService.java

You can click on each of the down arrows (⇩) to get a menu for finding usages, derived types, overrides…