* Added examples for java-9 filtering collector

core-java-9/src/main/java/com/baeldung/java9/language/stream/StreamsGroupingCollectionFilter.java

@@ -0,0 +1,27 @@
+package com.baeldung.java9.language.stream;
+
+import static java.util.stream.Collectors.filtering;
+import static java.util.stream.Collectors.groupingBy;
+import static java.util.stream.Collectors.toList;
+
+import java.util.Collection;
+import java.util.List;
+import java.util.Map;
+import java.util.function.Function;
+
+public class StreamsGroupingCollectionFilter {
+
+    static public Map<Integer, List<Integer>> findEvenNumbersAfterGroupingByQuantityOfDigits(Collection<Integer> baseCollection) {
+        Function<Integer, Integer> getQuantityOfDigits = item -> (int) Math.log10(item) + 1;
+
+        return baseCollection.stream()
+            .collect(groupingBy(getQuantityOfDigits, filtering(item -> item % 2 == 0, toList())));
+    }
+
+    static public Map<Integer, List<Integer>> findEvenNumbersBeforeGroupingByQuantityOfDigits(Collection<Integer> baseCollection) {
+
+        return baseCollection.stream()
+            .filter(item -> item % 2 == 0)
+            .collect(groupingBy(item -> (int) Math.log10(item) + 1, toList()));
+    }
+}