JDK8CompletableFuture创建
一、CompletableFuture替代Future+Callable完成更复杂的并发场景，使用completableFuture的使用就可以用then，when等等操作来防止Future以上的get阻塞和轮询isDone的现象出现，既可以表示一个完整的CompletableFuture，也可以表示CompletionStage阶段组合更复杂的阶段。
二、创建CompletableFuture的方式.
1、直接查看源码.
2、无返回+默认线程池ForkJoinPool
// 测试CompletableFuture的异步默认线程池方式
private static void testCompletableFuture(){
CompletableFuture completableFuture = CompletableFuture.runAsync(new Runnable() {
@Override
public void run() {
System.out.println("Thread：" + Thread.currentThread().getName());
}
});
// 阻塞主线程等待线程完成
completableFuture.join();
System.out.println("runAsync");
} 
3、无返回值+自定义线程池
// 测试CompletableFuture的异步默认线程池方式
private static void testCompletableFuture(){
ThreadPoolExecutor threadPoolExecutor=new ThreadPoolExecutor(5, 10, 30, TimeUnit.SECONDS, new ArrayBlockingQueue<>(100));
CompletableFuture completableFuture = CompletableFuture.runAsync(new Runnable() {
@Override
public void run() {
System.out.println("Thread：" + Thread.currentThread().getName());
}
},threadPoolExecutor);
// 阻塞主线程等待线程完成
completableFuture.join();
threadPoolExecutor.shutdown();
System.out.println("runAsync");
} 
4、有返回值+默认线程池.
// 测试CompletableFuture的异步默认线程池方式
private static void testCompletableFuture() throws ExecutionException, InterruptedException {
//ThreadPoolExecutor threadPoolExecutor=new ThreadPoolExecutor(5, 10, 30, TimeUnit.SECONDS, new ArrayBlockingQueue<>(100));
CompletableFuture completableFuture = CompletableFuture.supplyAsync(()->{
System.out.println("Thread：" + Thread.currentThread().getName());
return "CompletableFuture";
});
// 阻塞主线程等待线程完成
completableFuture.join();
System.out.println(completableFuture.get());
//threadPoolExecutor.shutdown();
System.out.println("runAsync");
} 
5、有返回值+自定义线程池.
// 测试CompletableFuture的异步默认线程池方式
private static void testCompletableFuture() throws ExecutionException, InterruptedException {
ThreadPoolExecutor threadPoolExecutor=new ThreadPoolExecutor(5, 10, 30, TimeUnit.SECONDS, new ArrayBlockingQueue<>(100));
CompletableFuture completableFuture = CompletableFuture.supplyAsync(()->{
System.out.println("Thread：" + Thread.currentThread().getName());
return "CompletableFuture+threadPoolExecutor";
},threadPoolExecutor);
// 阻塞主线程等待线程完成
completableFuture.join();
System.out.println(completableFuture.get());
threadPoolExecutor.shutdown();
System.out.println("supplyAsync");
} 
三、多接口并行优化实践。
1、Future+Callable+Executors
三个模拟的业务方法.
private static String getUserDomain() {
try {
TimeUnit.SECONDS.sleep(1);
} catch (InterruptedException e) {
e.printStackTrace();
}
return "getUserDomain";
}
private static String getBillTime() {
try {
TimeUnit.SECONDS.sleep(2);
} catch (InterruptedException e) {
e.printStackTrace();
}
return "getBillTime";
}
private static String getFlowData() {
try {
TimeUnit.SECONDS.sleep(3);
} catch (InterruptedException e) {
e.printStackTrace();
}
return "getFlowData";
} private static void getCallableResult() throws InterruptedException, ExecutionException {
// Callable+Executors+Future线程池方式
ExecutorService executorService = Executors.newFixedThreadPool(3);
long start = System.currentTimeMillis();
List> futureList = new ArrayList<>();
Future result1 = executorService.submit(new Callable() {
@Override
public String call() throws Exception {
return getUserDomain();
}
});
Future result2 = executorService.submit(new Callable() {
@Override
public String call() throws Exception {
return getFlowData();
}
});
Future result3 = executorService.submit(new Callable() {
@Override
public String call() throws Exception {
return getBillTime();
}
});
futureList.add(result1);
futureList.add(result2);
futureList.add(result3);
for (Future future : futureList) {
System.out.println("Result:" + future.get());
}
executorService.shutdown();
long end = System.currentTimeMillis();
System.out.println("共计耗时:" + (end - start)+"秒");
} 最终是响应最久的接口完成才完成最后计算结果。
2、CompletableFuture+Executor.
private static void getCompletableResult() throws ExecutionException, InterruptedException {
ExecutorService executorService = Executors.newFixedThreadPool(3);
long start = System.currentTimeMillis();
CompletableFuture completableFuture1 = CompletableFuture.supplyAsync(() ->
getUserDomain()
, executorService);
CompletableFuture completableFuture2 = CompletableFuture.supplyAsync(() ->
getBillTime()
, executorService);
CompletableFuture completableFuture3 = CompletableFuture.supplyAsync(() ->
getFlowData()
, executorService);
CompletableFuture.allOf(completableFuture1,completableFuture2,completableFuture3).join();
List completableList=new ArrayList<>();
completableList.add(completableFuture1.get());
completableList.add(completableFuture2.get());
completableList.add(completableFuture3.get());
System.out.println(completableList);
executorService.shutdown();
long end=System.currentTimeMillis();
System.out.println("Completable cost time: "+(end-start)+"S");
} 
API如下：
1、Supplier
2、Runnable，俺没有入参也没有返回值你说气人不？就是这么随心所欲。
3、CompletableFuture.allOf
allOf就是所有任务都完成时返回。但是是个Void的返回值。
4、anyOf是当入参的completableFuture组中有一个任务执行完毕就返回。返回结果是第一个完成的任务的结果。
5、join();挂起调用线程的执行，主线程调用了那个异步的任务，然后主线程挂起等待子线程完成在执行后面的喽
然后顺便看看Thread的join()方法.
至此了解CompletableFuture的基本创建，下一篇介绍then()和when()等的阶段计算，多看哈源码就大概知道了，而且影响深刻，奥利给。