add Cf08 demo:手动完成(complete/completeExceptionally/obtrudeValue/cancel)

src/main/java/space/anyi/Cf08_ManualComplete.java

@@ -0,0 +1,39 @@
+package space.anyi;
+
+import java.util.concurrent.CompletableFuture;
+
+public class Cf08_ManualComplete {
+    public static void main(String[] args) throws Exception {
+        // complete: 任务的完成时机由我们手动决定(比如等待外部事件/用户操作)
+        CompletableFuture<String> gate = new CompletableFuture<>();
+        new Thread(() -> {
+            try {
+                Thread.sleep(500);
+            } catch (InterruptedException e) {
+                e.printStackTrace();
+            }
+            gate.complete("外部线程触发了完成");
+        }).start();
+        System.out.println("阻塞等待手动完成: " + gate.join());
+
+        // completeExceptionally: 手动让任务以异常结束，常用于"超时兜底"
+        CompletableFuture<Integer> timeout = new CompletableFuture<>();
+        timeout.completeExceptionally(new RuntimeException("调用超时，兜底结束"));
+        try {
+            timeout.join();
+        } catch (Exception e) {
+            System.out.println("completeExceptionally 抛给调用方: " + e.getCause());
+        }
+
+        // obtrudeValue: 无论之前是否已完成，强制覆盖为新值(慎用)
+        CompletableFuture<String> forced = CompletableFuture.completedFuture("旧结果");
+        forced.obtrudeValue("强制更新的结果");
+        System.out.println("obtrudeValue 覆盖后: " + forced.join());
+
+        // cancel: 取消任务, isCancelled 与 isCompletedExceptionally 都会为 true
+        CompletableFuture<String> cancelling = new CompletableFuture<>();
+        System.out.println("cancel() 返回值: " + cancelling.cancel(true));
+        System.out.println("取消后 isCancelled: " + cancelling.isCancelled()
+                + ", isCompletedExceptionally: " + cancelling.isCompletedExceptionally());
+    }
+}