CompletableFuture - JiyangM/spring GitHub Wiki
public static CompletableFuture<Void> runAsync(Runnable runnable)
public static CompletableFuture<Void> runAsync(Runnable runnable, Executor executor)
public static <U> CompletableFuture<U> supplyAsync(Supplier<U> supplier)
public static <U> CompletableFuture<U> supplyAsync(Supplier<U> supplier, Executor executor)通过以上方法创建一个CompletableFuture，传一个Runnable或者Supplier对象，这个对象区别就是Runnable无返回值，而Supplier有返回值，然后再通过thenxxx()方法执行上一个CompletableFuture的执行结果，这个方法可实现异步执行而不会阻塞主线程：
public <U> CompletableFuture<U> thenApply(Function<? super T,? extends U> fn)
public <U> CompletableFuture<U> thenApplyAsync(Function<? super T,? extends U> fn)
public <U> CompletableFuture<U> thenApplyAsync(Function<? super T,? extends U> fn, Executor executor)public CompletableFuture<Void> thenAccept(Consumer<? super T> action)
public CompletableFuture<Void> thenAcceptAsync(Consumer<? super T> action)
public CompletableFuture<Void> thenAcceptAsync(Consumer<? super T> action, Executor executor)以上两类方法都可以异步执行，区别是转换有返回值，纯消费无返回值，通常出消费在异步执行链中的末端位置，执行最终的处理， 而转换通常处于还需要继续对执行结果进行下一步处理的时候用；无Async后缀的方法继续在当前线程处理，而有Async后缀的可以在其它线程处理上一个执行结果。
CompletableFuture<Void> future1 = CompletableFuture.runAsync(() -> {
try {
System.out.println("f1 开始");
Thread.sleep(4000L);
System.out.println("f1 睡完");
} catch (InterruptedException e) {
e.printStackTrace();
}
});
CompletableFuture<Void> futur2 = CompletableFuture.runAsync(() -> {
try {
System.out.println("f2 开始");
Thread.sleep(2000L);
System.out.println("f2 睡完");
} catch (InterruptedException e) {
e.printStackTrace();
}
});
CompletableFuture.allOf(futur2,future1).join();f1 开始
f2 开始
f2 睡完
f1 睡完Person person = new Person();
CompletableFuture<Person> personCompletableFuture1 =
CompletableFuture.completedFuture(person).thenApplyAsync(person1 -> {
try {
System.out.println("f1 开始");
Thread.sleep(2000L);
System.out.println("f1 睡完");
person1.setAge(20);
} catch (InterruptedException e) {
}
return person;
});
CompletableFuture<Person> personCompletableFuture2 =
CompletableFuture.completedFuture(person).thenApplyAsync(person1 -> {
try {
System.out.println("f2 开始");
Thread.sleep(4000L);
System.out.println("f2 睡完");
person1.setName("df");
} catch (InterruptedException e) {
}
return person;
});
CompletableFuture.allOf(personCompletableFuture1,personCompletableFuture2).join();
System.out.println(person.toString());f1 开始
f2 开始
f1 睡完
f2 睡完StringBuilder result = new StringBuilder();
List messages = Arrays.asList("a", "b", "c");
List<CompletableFuture> futures = messages.stream()
.map(msg -> CompletableFuture.completedFuture(msg).thenApplyAsync(
s -> delayedUpperCase(s)))
.collect(Collectors.toList());
CompletableFuture allOf = CompletableFuture.allOf(futures.toArray(new CompletableFuture[futures.size()]))
.whenComplete((v, th) -> {
futures.forEach(cf -> assertTrue(isUpperCase(cf.getNow(null))));
result.append("done");
});
allOf.join();
assertTrue("Result was empty", result.length() > 0);