add Cf07 demo:异常处理(exceptionally/whenComplete/handle)

src/main/java/space/anyi/Cf07_ExceptionHandling.java

@@ -0,0 +1,41 @@
+package space.anyi;
+
+import java.util.concurrent.CompletableFuture;
+
+public class Cf07_ExceptionHandling {
+    public static void main(String[] args) throws Exception {
+        // exceptionally: 任务失败时给出降级结果(类似异常被"恢复")
+        CompletableFuture<Integer> fallback = failTask().exceptionally(e -> {
+            System.out.println("exceptionally 捕获: " + e.getClass().getSimpleName());
+            return -1;   // 降级返回
+        });
+        System.out.println("exceptionally 降级结果: " + fallback.join());
+
+        // whenComplete: 只"观察"结果或异常，做了日志记录就够，
+        // 注意它不消化异常 —— 原任务失败，链上的 join/get 依然会抛 CompletionException
+        CompletableFuture<Integer> observed = failTask();
+        try {
+            observed.whenComplete((res, ex) -> {
+                if (ex != null) {
+                    System.out.println("whenComplete 观察到异常: " + ex.getClass().getSimpleName());
+                } else {
+                    System.out.println("whenComplete 观察到结果: " + res);
+                }
+            }).join();
+        } catch (Exception e) {
+            System.out.println("whenComplete 不吞异常, join() 抛: " + e.getClass().getSimpleName());
+        }
+
+        // handle: 无论成功失败都给一个函数处理，并可返回新结果(可恢复)
+        CompletableFuture<String> handled = failTask().handle((res, ex) ->
+                ex == null ? "正常结果: " + res : "出错被恢复: " + ex.getMessage());
+        System.out.println("handle 结果: " + handled.join());
+    }
+
+    private static CompletableFuture<Integer> failTask() {
+        return CompletableFuture.supplyAsync(() -> {
+            System.out.println("任务执行中...");
+            throw new RuntimeException("模拟异常");
+        });
+    }
+}