JAVA-2108: Move Introduction to Protonpack to the libraries-6 (eugenp#9673)

Author: kwoyke

core-java-modules/core-java-streams/README.md

@@ -9,7 +9,6 @@ This module contains articles about the Stream API in Java.
 - [Iterable to Stream in Java](https://www.baeldung.com/java-iterable-to-stream)
 - [How to Iterate Over a Stream With Indices](https://www.baeldung.com/java-stream-indices)
 - [Stream Ordering in Java](https://www.baeldung.com/java-stream-ordering)
-- [Introduction to Protonpack](https://www.baeldung.com/java-protonpack)
 - [Java Stream Filter with Lambda Expression](https://www.baeldung.com/java-stream-filter-lambda)
 - [Counting Matches on a Stream Filter](https://www.baeldung.com/java-stream-filter-count)
 - [Summing Numbers with Java Streams](https://www.baeldung.com/java-stream-sum)

libraries-6/README.md

@@ -14,4 +14,5 @@ Remember, for advanced libraries like [Jackson](/jackson) and [JUnit](/testing-m
 - [Introduction to Functional Java](https://www.baeldung.com/java-functional-library)
 - [A Guide to the Reflections Library](https://www.baeldung.com/reflections-library)
 - [Exactly Once Processing in Kafka](https://www.baeldung.com/kafka-exactly-once)
+- [Introduction to Protonpack](https://www.baeldung.com/java-protonpack)
 - More articles [[<-- prev]](/libraries-5)

core-java-modules/core-java-streams/src/test/java/com/baeldung/protonpack/ProtonpackUnitTest.java libraries-6/src/test/java/com/baeldung/protonpack/ProtonpackUnitTest.java

@@ -10,8 +10,6 @@
 import java.util.List;
 import java.util.Optional;
 import java.util.Set;
-import java.util.concurrent.atomic.AtomicInteger;
-import java.util.function.Function;
 import java.util.stream.Collectors;
 import java.util.stream.Stream;