completablefuture任务不能并行运行

pxy2qtax  于 2021-07-11  发布在  Java
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我在哪里有问题 CompletableFuture 循环中的任务不是并行运行,而是同步运行:

List<List<File>> filesLists = divideArrayIntoChunks(Arrays.asList(filesArray), 10);

        // number of tasks
        int numberOfTasks = filesLists.size();

        List<CompletableFuture<TreeMap<String, HashMap<String, Integer>>>> builderPartsMapFutures = Lists
                .newArrayList();

        for (int i = 0; i < numberOfTasks; i++) {

            List<File> filesList = filesLists.get(i);

            builderPartsMapFutures.add(getCompetableFutureResult(filesList, fileNameAndCharactersAmountMatchersMap,
                    namesElementsMap, namesAndFileNamesMatchingCharactersMap));
        }

        @SuppressWarnings("rawtypes")
        CompletableFuture[] futureResultArray = builderPartsMapFutures
                .toArray(new CompletableFuture[builderPartsMapFutures.size()]);

        CompletableFuture<Void> combinedFuture = CompletableFuture.allOf(futureResultArray);

        combinedFuture.get();

        CompletableFuture<List<TreeMap<String, HashMap<String, Integer>>>> finalResults = combinedFuture.thenApply(
                voidd -> builderPartsMapFutures.stream().map(future -> future.join()).collect(Collectors.toList()));

        finalResults.thenAccept(result -> System.out.println(result));

这是 getCompetableFutureResult() 方法:

public static CompletableFuture<TreeMap<String, HashMap<String, Integer>>> getCompetableFutureResult(
            List<File> filesList, HashMap<String, Integer> fileNameAndCharactersAmountMatchersMap,
            TreeMap<String, ArrayList<String>> namesElementsMap,
            TreeMap<String, Map<String, Integer>> namesAndFileNamesMatchingCharactersMap) {

        return CompletableFuture
                .supplyAsync(() -> buildNamesAndFileNamesWithMatchingCharactersMapForEachChunk(filesList,
                        fileNameAndCharactersAmountMatchersMap, namesElementsMap,
                        namesAndFileNamesMatchingCharactersMap));
    }
b1uwtaje

b1uwtaje1#

public static <U> CompletableFuture<U> supplyAsync(Supplier<U> supplier)

返回一个新的completablefuture,该Future由运行在forkjoinpool.commonpool()中的任务异步完成,其值通过调用给定的供应商获得。
https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/completablefuture.html#supplyasync-java.util.function.supplier供应商-
下面是代码中相同工作流的简化版本。

List<CompletableFuture<Integer>> futures = new ArrayList<>();

    for (int i = 0; i < 21; i++) {
        int finalI = i;
        futures.add(CompletableFuture.supplyAsync(() -> {
            System.out.println(finalI);
            return 3;
        }));
    }

    System.out.println("before running all of");
    CompletableFuture<Void> allOf = CompletableFuture.allOf(futures.toArray(new CompletableFuture[3]));
    try {
        allOf.get();
    } catch (InterruptedException | ExecutionException e) {
        e.printStackTrace();
    }

输出显示线程正在异步运行。它不是一个接一个的。

before running all of
0
1
2
5
3
9
10
4
14
11
16
6
15
13
12
20
7
19
18
17
8

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