https://commons.apache.org/proper/commons-io/apidocs/org/apache/commons/io/input/MessageDigestCalculatingInputStream.MessageDigestMaintainingObserver.html
MessageDigestCalculatingInputStream.MessageDigestMaintainingObserver (Apache Commons IO 2.22.0 API)
declaration: package: org.apache.commons.io.input, class: MessageDigestCalculatingInputStream, class: MessageDigestMaintainingObserver
apache commonsioapi