diff --git a/concurrency/src/main/java/io/mincong/concurrency/completablefuture/MultipleStageDemo.java b/concurrency/src/main/java/io/mincong/concurrency/completablefuture/MultipleStageDemo.java
new file mode 100644
index 00000000..e90e647b
--- /dev/null
+++ b/concurrency/src/main/java/io/mincong/concurrency/completablefuture/MultipleStageDemo.java
@@ -0,0 +1,205 @@
+package io.mincong.concurrency.completablefuture;
+
+import java.time.LocalTime;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.Executors;
+import java.util.stream.IntStream;
+
+public class MultipleStageDemo {
+
+ public static void main(String[] args) {
+ var demo = new MultipleStageDemo();
+ demo.scenario1();
+ demo.scenario2();
+ }
+
+ /**
+ * In scenario 1, resource creation and deletion are done in the same completion stage. Given a
+ * fixed thread pool executor with 2 threads, the executor will complete the tasks of two
+ * resources (e.g. 0 and 1) before starting the next stages. Its behavior can be illustrated as
+ * follows:
+ *
+ *
+ * +-----------------------------------------------------------------> Time
+ * | +------------------------+ +------------------------+
+ * Thread 1 | | Creation 0, Deletion 0 | | Creation 2, Deletion 2 |
+ * | +------------------------+ +------------------------+
+ * Thread 2 | | Creation 1, Deletion 1 | | Creation 3, Deletion 3 |
+ * | +------------------------+ +------------------------+
+ * |
+ *
+ *
+ * This is because these stages are queued in the following way:
+ *
+ *
+ * 0. +------------------------+
+ * | Creation 0, Deletion 0 |
+ * +------------------------+
+ * 1. +------------------------+
+ * | Creation 1, Deletion 1 |
+ * +------------------------+
+ * 2. +------------------------+
+ * | Creation 2, Deletion 2 |
+ * +------------------------+
+ * 3. +------------------------+
+ * | Creation 3, Deletion 3 |
+ * +------------------------+
+ *
+ *
+ * Console output:
+ *
+ *
+ * [15:41:18.010681][main] - Scenario 1 started
+ * [15:41:18.103478][pool-1-thread-1] - [id=0] New resource: creating
+ * [15:41:18.103482][pool-1-thread-2] - [id=1] New resource: creating
+ * [15:41:19.107141][pool-1-thread-1] - [id=0] New resource: created
+ * [15:41:19.107472][pool-1-thread-1] - [id=0] Old resource: creating
+ * [15:41:19.108780][pool-1-thread-2] - [id=1] New resource: created
+ * [15:41:19.108929][pool-1-thread-2] - [id=1] Old resource: creating
+ * [15:41:20.112909][pool-1-thread-2] - [id=1] Old resource: created
+ * [15:41:20.112909][pool-1-thread-1] - [id=0] Old resource: created
+ * [15:41:20.113265][pool-1-thread-1] - [id=2] New resource: creating
+ * [15:41:20.113452][pool-1-thread-2] - [id=3] New resource: creating
+ * [15:41:21.114555][pool-1-thread-1] - [id=2] New resource: created
+ * [15:41:21.114555][pool-1-thread-2] - [id=3] New resource: created
+ * [15:41:21.114914][pool-1-thread-1] - [id=2] Old resource: creating
+ * [15:41:21.115019][pool-1-thread-2] - [id=3] Old resource: creating
+ * [15:41:22.119584][pool-1-thread-2] - [id=3] Old resource: created
+ * [15:41:22.119584][pool-1-thread-1] - [id=2] Old resource: created
+ * [15:41:22.120209][main] - Scenario 1 finished
+ *
+ */
+ private void scenario1() {
+ print("Scenario 1 started");
+ var executor = Executors.newFixedThreadPool(2);
+ var futures =
+ IntStream.range(0, 4)
+ .mapToObj(
+ i ->
+ CompletableFuture.runAsync(
+ () -> {
+ createNewResource(i);
+ deleteOldResource(i);
+ },
+ executor))
+ .toArray(CompletableFuture[]::new);
+ try {
+ CompletableFuture.allOf(futures).join();
+ } finally {
+ executor.shutdownNow();
+ }
+ print("Scenario 1 finished");
+ }
+
+ /**
+ * In scenario 2, resource creation and deletion are done separately in two completion stages.
+ * Given a fixed thread pool executor with 2 threads, the executor will complete the creation of
+ * two resources (e.g. 0 and 1) then continue the creation of two other resources (e.g. 2 and 3).
+ * Once done, it will start the deletions in the same way.
+ *
+ *
+ * +-----------------------------------------------------------------> Time
+ * | +------------+ +------------+ +------------+ +------------+
+ * Thread 1 | | Creation 0 | | Creation 2 | | Deletion 0 | | Deletion 2 |
+ * | +------------+ +------------+ +------------+ +------------+
+ * Thread 2 | | Creation 1 | | Creation 3 | | Deletion 1 | | Deletion 3 |
+ * | +------------+ +------------+ +------------+ +------------+
+ * |
+ *
+ *
+ * This is because these stages are queued in the following way:
+ *
+ *
+ * 0. +------------+
+ * | Creation 0 |
+ * +------------+
+ * 1. +------------+
+ * | Creation 1 |
+ * +------------+
+ * 2. +------------+
+ * | Creation 2 |
+ * +------------+
+ * 3. +------------+
+ * | Creation 3 |
+ * +------------+
+ * 4. +------------+
+ * | Deletion 0 |
+ * +------------+
+ * 5. +------------+
+ * | Deletion 1 |
+ * +------------+
+ * 6. +------------+
+ * | Deletion 2 |
+ * +------------+
+ * 7. +------------+
+ * | Deletion 3 |
+ * +-------------+
+ *
+ *
+ * Console output:
+ *
+ *
+ * [15:41:22.120374][main] - Scenario 2 started
+ * [15:41:22.123783][pool-2-thread-1] - [id=0] New resource: creating
+ * [15:41:22.124870][pool-2-thread-2] - [id=1] New resource: creating
+ * [15:41:23.126835][pool-2-thread-1] - [id=0] New resource: created
+ * [15:41:23.126927][pool-2-thread-2] - [id=1] New resource: created
+ * [15:41:23.127811][pool-2-thread-1] - [id=2] New resource: creating
+ * [15:41:23.127868][pool-2-thread-2] - [id=3] New resource: creating
+ * [15:41:24.132029][pool-2-thread-2] - [id=3] New resource: created
+ * [15:41:24.132044][pool-2-thread-1] - [id=2] New resource: created
+ * [15:41:24.132439][pool-2-thread-2] - [id=0] Old resource: creating
+ * [15:41:24.132452][pool-2-thread-1] - [id=1] Old resource: creating
+ * [15:41:25.137506][pool-2-thread-2] - [id=0] Old resource: created
+ * [15:41:25.137506][pool-2-thread-1] - [id=1] Old resource: created
+ * [15:41:25.137804][pool-2-thread-2] - [id=3] Old resource: creating
+ * [15:41:25.138011][pool-2-thread-1] - [id=2] Old resource: creating
+ * [15:41:26.138201][pool-2-thread-2] - [id=3] Old resource: created
+ * [15:41:26.138340][pool-2-thread-1] - [id=2] Old resource: created
+ * [15:41:26.139091][main] - Scenario 2 finished
+ *
+ */
+ private void scenario2() {
+ print("Scenario 2 started");
+ var executor = Executors.newFixedThreadPool(2);
+ var futures =
+ IntStream.range(0, 4)
+ .mapToObj(
+ i ->
+ CompletableFuture.runAsync(() -> createNewResource(i), executor)
+ .thenRunAsync(() -> deleteOldResource(i), executor))
+ .toArray(CompletableFuture[]::new);
+ try {
+ CompletableFuture.allOf(futures).join();
+ } finally {
+ executor.shutdownNow();
+ }
+ print("Scenario 2 finished");
+ }
+
+ private void createNewResource(int i) {
+ print("[id=" + i + "] New resource: creating");
+ try {
+ Thread.sleep(1000);
+ } catch (InterruptedException e) {
+ // ignore
+ }
+ print("[id=" + i + "] New resource: created");
+ }
+
+ private void deleteOldResource(int i) {
+ print("[id=" + i + "] Old resource: creating");
+ try {
+ Thread.sleep(1000);
+ } catch (InterruptedException e) {
+ // ignore
+ }
+ print("[id=" + i + "] Old resource: created");
+ }
+
+ private static void print(String message) {
+ var thread = Thread.currentThread().getName();
+ var time = LocalTime.now();
+ System.out.println("[" + time + "][" + thread + "] - " + message);
+ }
+}