diff --git a/src/test/java/lambdas/CollectionsTest.java b/src/test/java/lambdas/CollectionsTest.java
new file mode 100644
index 0000000..ade57cf
--- /dev/null
+++ b/src/test/java/lambdas/CollectionsTest.java
@@ -0,0 +1,39 @@
+package lambdas;
+
+import org.junit.jupiter.api.Test;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.stream.Collectors;
+
+public class CollectionsTest {
+
+    @Test
+    void forEach_with_collections() {
+        List<String> strings = List.of("this", "is", "a", "list", "of", "strings");
+        List<Integer> lengths = new ArrayList<>();
+
+        // Old school, but may have concurrency issues
+        for (String string : strings) {
+            lengths.add(string.length());
+        }
+        System.out.println(lengths);
+
+        // functional way (collect respects "order")
+        lengths = strings.parallelStream()
+                .peek(x -> System.out.println(x + "on thread " + Thread.currentThread().getName()))
+                .map(String::length)
+                .collect(Collectors.toList());
+        System.out.println(lengths);
+
+        // forEach does NOT respect order
+        List<Integer> stringLengths = new ArrayList<>();
+        strings.parallelStream().forEachOrdered( str -> stringLengths.add(str.length()));
+        System.out.println(stringLengths);
+
+        Map<String, Integer> map = Map.of("a", 1, "b", 2, "c", 2);
+        map.forEach((key, value) -> System.out.println(key + ": " + value));
+    }
+}