completableFuture使用

1、runAsync（Runnable） 异步方法，默认线程池，无返回值
2、runAsync（Runnable，Executor） 异步方法,自定义线程池，无返回值

public static void main(String[] args) {
       System.out.println("test start");
       CompletableFuture.runAsync(() -> {  System.out.println("test runAsync");});

       ExecutorService executors =  Executors.newFixedThreadPool(1);
       CompletableFuture.runAsync(() -> {  System.out.println("test runAsync with executors");},executors);
   }

输出结果：
test start
test runAsync
test runAsync with executors

3、runAsync（Runnable） 异步方法，默认线程池，有返回值
4、runAsync（Runnable，Executor） 异步方法,自定义线程池，有返回值

public static void main(String[] args) {
        System.out.println("test start");
        CompletableFuture<String> test1 = CompletableFuture.supplyAsync(() -> {  System.out.println("test supplyAsync");return "zhao";});
        System.out.println(test1.join());

        ExecutorService executors =  Executors.newFixedThreadPool(1);
        CompletableFuture<String> test2 = CompletableFuture.supplyAsync(() -> {  System.out.println("test supplyAsync with executors");return "lao tuo";},executors);
        System.out.println(test2.join());
    }

输出结果：
test start
test supplyAsync
zhao
test supplyAsync with executors
lao tuo

5、join，get
都是获取异步线程执行结果，例如上面例子；阻塞线程等待异步结果
但是get抛出来检查异常

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    public static void main(String[] args) throws ExecutionException, InterruptedException {
        System.out.println("test start");
        CompletableFuture<String> test1 = CompletableFuture.supplyAsync(() -> {  System.out.println("test supplyAsync");return "zhao";});
        System.out.println(test1.join());

        ExecutorService executors =  Executors.newFixedThreadPool(1);
        CompletableFuture<String> test2 = CompletableFuture.supplyAsync(() -> {  System.out.println("test supplyAsync with executors");return "lao tuo";},executors);
        System.out.println(test2.get());
    }

6、thenApply方法
使用thenApply来将两个线程串行化，如果任务出现异常不会执行thenApply

public static void main(String[] args) {
        System.out.println("test start");
        CompletableFuture<String> test1 = CompletableFuture.supplyAsync(() -> {
            System.out.println("test supplyAsync");
            return "zhao";
        }).thenApply(then ->{
            return then+" lao tuo";
        });
        System.out.println(test1.join());
    }

输出结果：
test start
test supplyAsync
zhao lao tuo

如果thenApply 执行线程需要异步化，使用thenApplyAsync

 public static void main(String[] args) {
        System.out.println("test start");
        CompletableFuture<String> test1 = CompletableFuture.supplyAsync(() -> {
            System.out.println("test supplyAsync");
            return "zhao";
        }).thenApplyAsync(then ->{
            return then+" lao tuo";
        });
        System.out.println(test1.join()); }

7、handle方法
执行任务完成后对结果处理，可以根据任务是否异常来做处理

    public static void main(String[] args) {
        System.out.println("test start");
        CompletableFuture<String> test1 = CompletableFuture.supplyAsync(() -> {
            System.out.println("test supplyAsync");
            int a = 1/0;
            return "zhao";
        }).handle((t,throwable) ->{
            if(throwable != null){
                System.out.println(throwable);
            }else {
                t = t + " lao tuo";
            }
            return t;
        });
        System.out.println(test1.join());
    }

输出结果：
test start
test supplyAsync
java.util.concurrent.CompletionException: java.lang.ArithmeticException: / by zero
null

8、thenCombine方法
会将两个线程执行万，调用者线程会将两个异步任务的结果一块处理

 public static void main(String[] args) {
        System.out.println("test start");
        CompletableFuture<String> test1 = CompletableFuture.supplyAsync(() -> {
            System.out.println("test supplyAsync");
            return "zhao";
        });
        CompletableFuture<String> test2 = CompletableFuture.supplyAsync(() -> {
            System.out.println("test supplyAsync");
            return " lao tuo ";
        });

        CompletableFuture<String> result = test1.thenCombine(test2,(result1,result2) ->{
            return result1+result2;
        });
        System.out.println(result.join());
    }

输出结果：
test start
test supplyAsync
test supplyAsync
zhao lao tuo

如果想要异步执行使用方法thenCombineAsync

9、thenCombine方法
第一个任务完成之后，将第一个任务结果作为参数传给第二个任务

  public static void main(String[] args) {
        System.out.println("test start");
        CompletableFuture<String> test1 = CompletableFuture.supplyAsync(() -> {
            System.out.println("test supplyAsync");
            return "zhao";
        }).thenCompose(result1 ->{
            return CompletableFuture.supplyAsync(() -> {
                System.out.println("test supplyAsync");
                return result1 + " lao tuo";
            });
        });
        System.out.println(test1.join());
    }

输出结果：
test start
test supplyAsync
test supplyAsync
zhao lao tuo