Java8 - 自定义实现体会CompletableFuture的原理

不念不忘少年蓝@ 2022-11-16 01:47 123阅读 0赞

### 文章目录 ###

*  Code

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3lhbmdzaGFuZ3dlaQ_size_16_color_FFFFFF_t_70]

--------------------

# Code #

Future 接口 的局限性有很多，其中一个就是需要主动的去询问是否完成，如果等子线程的任务完成以后，通知我，那岂不是更好？

public class FutureInAction3 { 
    
    
        public static void main(String[] args) { 
    
    
            Future<String> future = invoke(() -> { 
                try { 
                    Thread.sleep(10000L);
                    return "I am Finished.";
                } catch (InterruptedException e) { 
                    return "I am Error";
                }
            });
    
    
            future.setCompletable(new Completable<String>() { 
                @Override
                public void complete(String s) { 
                    System.out.println("complete called ---- " + s);
                }
    
                @Override
                public void exception(Throwable cause) { 
                    System.out.println("error");
                    cause.printStackTrace();
                }
            });
            System.out.println("....do something else .....");
            System.out.println("try to get result ->" + future.get());
        }
    
        private static <T> Future<T> invoke(Callable<T> callable) { 
    
            AtomicReference<T> result = new AtomicReference<>();
            AtomicBoolean finished = new AtomicBoolean(false);
    
            Future<T> future = new Future<T>() { 
                private Completable<T> completable;
    
                @Override
                public T get() { 
                    return result.get();
                }
    
                @Override
                public boolean isDone() { 
                    return finished.get();
                }
    
                // 设置完成
                @Override
                public void setCompletable(Completable<T> completable) { 
                    this.completable = completable;
                }
    
                // 获取
                @Override
                public Completable<T> getCompletable() { 
                    return completable;
                }
            };
            Thread t = new Thread(() -> { 
                try { 
                    T value = callable.action();
                    result.set(value);
                    finished.set(true);
                    if (future.getCompletable() != null)
                        future.getCompletable().complete(value);
                } catch (Throwable cause) { 
                    if (future.getCompletable() != null)
                        future.getCompletable().exception(cause);
                }
            });
            t.start();
    
            return future;
        }
    
    
        private interface Future<T> { 
    
            T get();
    
            boolean isDone();
    
            // 1
            void setCompletable(Completable<T> completable);
    
            // 2
            Completable<T> getCompletable();
        }
    
        private interface Callable<T> { 
            T action();
        }
    
        // 回调接口
        private interface Completable<T> { 
    
            void complete(T t);
    
            void exception(Throwable cause);
        }
    }

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3lhbmdzaGFuZ3dlaQ_size_16_color_FFFFFF_t_70 1]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3lhbmdzaGFuZ3dlaQ_size_16_color_FFFFFF_t_70]: /images/20221022/2d2e6a653a2341b58921acbcb11422d7.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3lhbmdzaGFuZ3dlaQ_size_16_color_FFFFFF_t_70 1]: /images/20221022/c54f0631d8f344c4a8a9f37b4f52b985.png