1、 runAsync 和 supplyAsync方法
CompletableFuture 提供了四个静态方法来创建一个异步操作。
1 public static CompletableFuture<Void> runAsync(Runnable runnable) 2 public static CompletableFuture<Void> runAsync(Runnable runnable, Executor executor) 3 public static <U> CompletableFuture<U> supplyAsync(Supplier<U> supplier) 4 public static <U> CompletableFuture<U> supplyAsync(Supplier<U> supplier, Executor executor)
没有指定Executor的方法会使用ForkJoinPool.commonPool() 作为它的线程池执行异步代码。如果指定线程池，则使用指定的线程池运行。以下所有的方法都类同。
- runAsync方法不支持返回值。
- supplyAsync可以支持返回值。
示例
1 //无返回值 2 public static void runAsync() throws Exception { 3 CompletableFuture<Void> future = CompletableFuture.runAsync(() -> { 4 try { 5 TimeUnit.SECONDS.sleep(1); 6 } catch (InterruptedException e) { 7 } 8 System.out.println("run end ..."); 9 }); 10 11 future.get(); 12 } 13 14 //有返回值 15 public static void supplyAsync() throws Exception { 16 CompletableFuture<Long> future = CompletableFuture.supplyAsync(() -> { 17 try { 18 TimeUnit.SECONDS.sleep(1); 19 } catch (InterruptedException e) { 20 } 21 System.out.println("run end ..."); 22 return System.currentTimeMillis(); 23 }); 24 25 long time = future.get(); 26 System.out.println("time = "+time); 27 }
2、计算结果完成时的回调方法
当CompletableFuture的计算结果完成，或者抛出异常的时候，可以执行特定的Action。主要是下面的方法：
1 public CompletableFuture<T> whenComplete(BiConsumer<? super T,? super Throwable> action) 2 public CompletableFuture<T> whenCompleteAsync(BiConsumer<? super T,? super Throwable> action) 3 public CompletableFuture<T> whenCompleteAsync(BiConsumer<? super T,? super Throwable> action, Executor executor) 4 public CompletableFuture<T> exceptionally(Function<Throwable,? extends T> fn)
可以看到Action的类型是BiConsumer<? super T,? super Throwable>它可以处理正常的计算结果，或者异常情况。
whenComplete 和 whenCompleteAsync 的区别：
whenComplete：是执行当前任务的线程执行继续执行 whenComplete 的任务。
whenCompleteAsync：是执行把 whenCompleteAsync 这个任务继续提交给线程池来进行执行。
示例
1 public static void whenComplete() throws Exception {
2 CompletableFuture<Void> future = CompletableFuture.runAsync(() -> {
3 try {
4 TimeUnit.SECONDS.sleep(1);
5 } catch (InterruptedException e) {
6 }
7 if(new Random().nextInt()%2>=0) {
8 int i = 12/0;
9 }
10 System.out.println("run end ...");
11 });
12
13 future.whenComplete(new BiConsumer<Void, Throwable>() {
14 @Override
15 public void accept(Void t, Throwable action) {
16 System.out.println("执行完成！");
17 }
18
19 });
20 future.exceptionally(new Function<Throwable, Void>() {
21 @Override
22 public Void apply(Throwable t) {
23 System.out.println("执行失败！"+t.getMessage());
24 return null;
25 }
26 });
27
28 TimeUnit.SECONDS.sleep(2);
29 }
3、 thenApply 方法
当一个线程依赖另一个线程时，可以使用 thenApply 方法来把这两个线程串行化。
1 public <U> CompletableFuture<U> thenApply(Function<? super T,? extends U> fn)
2 public <U> CompletableFuture<U> thenApplyAsync(Function<? super T,? extends U> fn)
3 public <U> CompletableFuture<U> thenApplyAsync(Function<? super T,? extends U> fn, Executor executor)
Function<? super T,? extends U>
T：上一个任务返回结果的类型
U：当前任务的返回值类型
示例
1 private static void thenApply() throws Exception {
2 CompletableFuture<Long> future = CompletableFuture.supplyAsync(new Supplier<Long>() {
3 @Override
4 public Long get() {
5 long result = new Random().nextInt(100);
6 System.out.println("result1="+result);
7 return result;
8 }
9 }).thenApply(new Function<Long, Long>() {
10 @Override
11 public Long apply(Long t) {
12 long result = t*5;
13 System.out.println("result2="+result);
14 return result;
15 }
16 });
17
18 long result = future.get();
19 System.out.println(result);
20 }
4、 handle 方法
handle 是执行任务完成时对结果的处理。
handle 方法和 thenApply 方法处理方式基本一样。不同的是 handle 是在任务完成后再执行，还可以处理异常的任务。thenApply 只可以执行正常的任务，任务出现异常则不执行 thenApply 方法。
1 public <U> CompletionStage<U> handle(BiFunction<? super T, Throwable, ? extends U> fn);
2 public <U> CompletionStage<U> handleAsync(BiFunction<? super T, Throwable, ? extends U> fn);
3 public <U> CompletionStage<U> handleAsync(BiFunction<? super T, Throwable, ? extends U> fn,Executor executor);
示例
1 public static void handle() throws Exception{
2 CompletableFuture<Integer> future = CompletableFuture.supplyAsync(new Supplier<Integer>() {
3
4 @Override
5 public Integer get() {
6 int i= 10/0;
7 return new Random().nextInt(10);
8 }
9 }).handle(new BiFunction<Integer, Throwable, Integer>() {
10 @Override
11 public Integer apply(Integer param, Throwable throwable) {
12 int result = -1;
13 if(throwable==null){
14 result = param * 2;
15 }else{
16 System.out.println(throwable.getMessage());
17 }
18 return result;
19 }
20 });
21 System.out.println(future.get());
22 }
从示例中可以看出，在 handle 中可以根据任务是否有异常来进行做相应的后续处理操作。而 thenApply 方法，如果上个任务出现错误，则不会执行 thenApply 方法。
5、 thenAccept 消费处理结果
接收任务的处理结果，并消费处理，无返回结果。
1 public CompletionStage<Void> thenAccept(Consumer<? super T> action);
2 public CompletionStage<Void> thenAcceptAsync(Consumer<? super T> action);
3 public CompletionStage<Void> thenAcceptAsync(Consumer<? super T> action,Executor executor);
示例
1 public static void thenAccept() throws Exception{
2 CompletableFuture<Void> future = CompletableFuture.supplyAsync(new Supplier<Integer>() {
3 @Override
4 public Integer get() {
5 return new Random().nextInt(10);
6 }
7 }).thenAccept(integer -> {
8 System.out.println(integer);
9 });
10 future.get();
11 }
从示例代码中可以看出，该方法只是消费执行完成的任务，并可以根据上面的任务返回的结果进行处理。并没有后续的输错操作。
6、thenRun 方法
跟 thenAccept 方法不一样的是，不关心任务的处理结果。只要上面的任务执行完成，就开始执行 thenAccept 。
public CompletionStage<Void> thenRun(Runnable action);
public CompletionStage<Void> thenRunAsync(Runnable action);
public CompletionStage<Void> thenRunAsync(Runnable action,Executor executor);
示例
public static void thenRun() throws Exception{
CompletableFuture<Void> future = CompletableFuture.supplyAsync(new Supplier<Integer>() {
@Override
public Integer get() {
return new Random().nextInt(10);
}
}).thenRun(() -> {
System.out.println("thenRun ...");
});
future.get();
}
该方法同 thenAccept 方法类似。不同的是上个任务处理完成后，并不会把计算的结果传给 thenRun 方法。只是处理玩任务后，执行 thenAccept 的后续操作。
7、thenCombine 合并任务
thenCombine 会把 两个 CompletionStage 的任务都执行完成后，把两个任务的结果一块交给 thenCombine 来处理。
1 public <U,V> CompletionStage<V> thenCombine(CompletionStage<? extends U> other,BiFunction<? super T,? super U,? extends V> fn); 2 public <U,V> CompletionStage<V> thenCombineAsync(CompletionStage<? extends U> other,BiFunction<? super T,? super U,? extends V> fn); 3 public <U,V> CompletionStage<V> thenCombineAsync(CompletionStage<? extends U> other,BiFunction<? super T,? super U,? extends V> fn,Executor executor);
示例
1 private static void thenCombine() throws Exception {
2 CompletableFuture<String> future1 = CompletableFuture.supplyAsync(new Supplier<String>() {
3 @Override
4 public String get() {
5 return "hello";
6 }
7 });
8 CompletableFuture<String> future2 = CompletableFuture.supplyAsync(new Supplier<String>() {
9 @Override
10 public String get() {
11 return "hello";
12 }
13 });
14 CompletableFuture<String> result = future1.thenCombine(future2, new BiFunction<String, String, String>() {
15 @Override
16 public String apply(String t, String u) {
17 return t+" "+u;
18 }
19 });
20 System.out.println(result.get());
21 }
8、thenAcceptBoth
当两个CompletionStage都执行完成后，把结果一块交给thenAcceptBoth来进行消耗
1 public <U> CompletionStage<Void> thenAcceptBoth(CompletionStage<? extends U> other,BiConsumer<? super T, ? super U> action); 2 public <U> CompletionStage<Void> thenAcceptBothAsync(CompletionStage<? extends U> other,BiConsumer<? super T, ? super U> action); 3 public <U> CompletionStage<Void> thenAcceptBothAsync(CompletionStage<? extends U> other,BiConsumer<? super T, ? super U> action, Executor executor);
示例
1 private static void thenAcceptBoth() throws Exception {
2 CompletableFuture<Integer> f1 = CompletableFuture.supplyAsync(new Supplier<Integer>() {
3 @Override
4 public Integer get() {
5 int t = new Random().nextInt(3);
6 try {
7 TimeUnit.SECONDS.sleep(t);
8 } catch (InterruptedException e) {
9 e.printStackTrace();
10 }
11 System.out.println("f1="+t);
12 return t;
13 }
14 });
15
16 CompletableFuture<Integer> f2 = CompletableFuture.supplyAsync(new Supplier<Integer>() {
17 @Override
18 public Integer get() {
19 int t = new Random().nextInt(3);
20 try {
21 TimeUnit.SECONDS.sleep(t);
22 } catch (InterruptedException e) {
23 e.printStackTrace();
24 }
25 System.out.println("f2="+t);
26 return t;
27 }
28 });
29 f1.thenAcceptBoth(f2, new BiConsumer<Integer, Integer>() {
30 @Override
31 public void accept(Integer t, Integer u) {
32 System.out.println("f1="+t+";f2="+u+";");
33 }
34 });
35 }
9、applyToEither 方法
两个CompletionStage，谁执行返回的结果快，我就用那个CompletionStage的结果进行下一步的转化操作。
1 public <U> CompletionStage<U> applyToEither(CompletionStage<? extends T> other,Function<? super T, U> fn);
2 public <U> CompletionStage<U> applyToEitherAsync(CompletionStage<? extends T> other,Function<? super T, U> fn);
3 public <U> CompletionStage<U> applyToEitherAsync(CompletionStage<? extends T> other,Function<? super T, U> fn,Executor executor);
示例
1 private static void applyToEither() throws Exception {
2 CompletableFuture<Integer> f1 = CompletableFuture.supplyAsync(new Supplier<Integer>() {
3 @Override
4 public Integer get() {
5 int t = new Random().nextInt(3);
6 try {
7 TimeUnit.SECONDS.sleep(t);
8 } catch (InterruptedException e) {
9 e.printStackTrace();
10 }
11 System.out.println("f1="+t);
12 return t;
13 }
14 });
15 CompletableFuture<Integer> f2 = CompletableFuture.supplyAsync(new Supplier<Integer>() {
16 @Override
17 public Integer get() {
18 int t = new Random().nextInt(3);
19 try {
20 TimeUnit.SECONDS.sleep(t);
21 } catch (InterruptedException e) {
22 e.printStackTrace();
23 }
24 System.out.println("f2="+t);
25 return t;
26 }
27 });
28
29 CompletableFuture<Integer> result = f1.applyToEither(f2, new Function<Integer, Integer>() {
30 @Override
31 public Integer apply(Integer t) {
32 System.out.println(t);
33 return t * 2;
34 }
35 });
36
37 System.out.println(result.get());
38 }
10、acceptEither 方法
两个CompletionStage，谁执行返回的结果快，我就用那个CompletionStage的结果进行下一步的消耗操作。
1 public CompletionStage<Void> acceptEither(CompletionStage<? extends T> other,Consumer<? super T> action);
2 public CompletionStage<Void> acceptEitherAsync(CompletionStage<? extends T> other,Consumer<? super T> action);
3 public CompletionStage<Void> acceptEitherAsync(CompletionStage<? extends T> other,Consumer<? super T> action,Executor executor);
示例
private static void acceptEither() throws Exception {
CompletableFuture<Integer> f1 = CompletableFuture.supplyAsync(new Supplier<Integer>() {
@Override
public Integer get() {
int t = new Random().nextInt(3);
try {
TimeUnit.SECONDS.sleep(t);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println("f1="+t);
return t;
}
});
CompletableFuture<Integer> f2 = CompletableFuture.supplyAsync(new Supplier<Integer>() {
@Override
public Integer get() {
int t = new Random().nextInt(3);
try {
TimeUnit.SECONDS.sleep(t);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println("f2="+t);
return t;
}
});
f1.acceptEither(f2, new Consumer<Integer>() {
@Override
public void accept(Integer t) {
System.out.println(t);
}
});
}
11、runAfterEither 方法
两个CompletionStage，任何一个完成了都会执行下一步的操作（Runnable）
1 public CompletionStage<Void> runAfterEither(CompletionStage<?> other,Runnable action);
2 public CompletionStage<Void> runAfterEitherAsync(CompletionStage<?> other,Runnable action);
3 public CompletionStage<Void> runAfterEitherAsync(CompletionStage<?> other,Runnable action,Executor executor);
示例
1 private static void runAfterEither() throws Exception {
2 CompletableFuture<Integer> f1 = CompletableFuture.supplyAsync(new Supplier<Integer>() {
3 @Override
4 public Integer get() {
5 int t = new Random().nextInt(3);
6 try {
7 TimeUnit.SECONDS.sleep(t);
8 } catch (InterruptedException e) {
9 e.printStackTrace();
10 }
11 System.out.println("f1="+t);
12 return t;
13 }
14 });
15
16 CompletableFuture<Integer> f2 = CompletableFuture.supplyAsync(new Supplier<Integer>() {
17 @Override
18 public Integer get() {
19 int t = new Random().nextInt(3);
20 try {
21 TimeUnit.SECONDS.sleep(t);
22 } catch (InterruptedException e) {
23 e.printStackTrace();
24 }
25 System.out.println("f2="+t);
26 return t;
27 }
28 });
29 f1.runAfterEither(f2, new Runnable() {
30
31 @Override
32 public void run() {
33 System.out.println("上面有一个已经完成了。");
34 }
35 });
36 }
12、runAfterBoth
两个CompletionStage，都完成了计算才会执行下一步的操作（Runnable）
1 public CompletionStage<Void> runAfterBoth(CompletionStage<?> other,Runnable action);
2 public CompletionStage<Void> runAfterBothAsync(CompletionStage<?> other,Runnable action);
3 public CompletionStage<Void> runAfterBothAsync(CompletionStage<?> other,Runnable action,Executor executor);
示例
1 private static void runAfterBoth() throws Exception {
2 CompletableFuture<Integer> f1 = CompletableFuture.supplyAsync(new Supplier<Integer>() {
3 @Override
4 public Integer get() {
5 int t = new Random().nextInt(3);
6 try {
7 TimeUnit.SECONDS.sleep(t);
8 } catch (InterruptedException e) {
9 e.printStackTrace();
10 }
11 System.out.println("f1="+t);
12 return t;
13 }
14 });
15
16 CompletableFuture<Integer> f2 = CompletableFuture.supplyAsync(new Supplier<Integer>() {
17 @Override
18 public Integer get() {
19 int t = new Random().nextInt(3);
20 try {
21 TimeUnit.SECONDS.sleep(t);
22 } catch (InterruptedException e) {
23 e.printStackTrace();
24 }
25 System.out.println("f2="+t);
26 return t;
27 }
28 });
29 f1.runAfterBoth(f2, new Runnable() {
30
31 @Override
32 public void run() {
33 System.out.println("上面两个任务都执行完成了。");
34 }
35 });
36 }
13、thenCompose 方法
thenCompose 方法允许你对两个 CompletionStage 进行流水线操作，第一个操作完成时，将其结果作为参数传递给第二个操作。
1 public <U> CompletableFuture<U> thenCompose(Function<? super T, ? extends CompletionStage<U>> fn);
2 public <U> CompletableFuture<U> thenComposeAsync(Function<? super T, ? extends CompletionStage<U>> fn) ;
3 public <U> CompletableFuture<U> thenComposeAsync(Function<? super T, ? extends CompletionStage<U>> fn, Executor executor) ;
示例
1 private static void thenCompose() throws Exception {
2 CompletableFuture<Integer> f = CompletableFuture.supplyAsync(new Supplier<Integer>() {
3 @Override
4 public Integer get() {
5 int t = new Random().nextInt(3);
6 System.out.println("t1="+t);
7 return t;
8 }
9 }).thenCompose(new Function<Integer, CompletionStage<Integer>>() {
10 @Override
11 public CompletionStage<Integer> apply(Integer param) {
12 return CompletableFuture.supplyAsync(new Supplier<Integer>() {
13 @Override
14 public Integer get() {
15 int t = param *2;
16 System.out.println("t2="+t);
17 return t;
18 }
19 });
20 }
21
22 });
23 System.out.println("thenCompose result : "+f.get());
24 }