completableFeature-demo/src/main/java/space/anyi/Cf08_ManualComplete.java

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());
    }
}