在Java8循环中转换旧循环

Question

我是Java8的新手，我有这段代码

for (Menu menu : resto1.getMenu()) {
    MainIngredient mainIngredient = MainIngredient.getMainIngredient(menu.getName());
}

我想重构以使其更快，并且我想将其转换为

List<CompletableFuture<MainIngredient>>

我尝试过

List<CompletableFuture<MainIngredient>> priceFutureList = resto1.getMenu().stream()
            map(menu -> CompletableFuture.supplyAsync(() -> MainIngredient.getMainIngredient(menu.getName()), executorService));

但我收到此错误：

 Type mismatch: cannot convert from Stream<Menu> to 
     List<CompletableFuture<MainIngredient>>

然后我也尝试过

CompletableFuture<List<MainIngredient>> mainIngredient =        
    CompletableFuture
        .supplyAsync(() ->  resto1.getMenu()
                                .stream()
                                .map(menu -> MainIngredient.getMainIngredient(menu.getName()))
                                .collect(Collectors.toList()), executorService);

但是我得到了CompletableFuture<List<MainIngredient>>而不是List<CompletableFuture<MainIngredient>>

Answer 1

在第一个解决方案中，您缺少collect(toList())：

List<CompletableFuture<MainIngredient>> priceFutureList = resto1.getMenu().stream()
            .map(menu -> CompletableFuture.supplyAsync(() -> MainIngredient.getMainIngredient(menu.getName()), executorService))
            .collect(Collectors.toList());