如何使用 CompletableFuture 将此代码转换为 Java 8 中的异步代码？ 我正在使用 Spring 引导

Question

Here is the Code Snippet that needs to be made async:

List<Course> courses = Lists.newArrayList();
Map<String, Map<String, Student>> result = Maps.newHashMap();

for (Map<String, Object> map : jsonObject) {
   courses.add(getCourse(map, fee));  
   result.put(map.get(GROUP), getInfoMap(map));  
}

PS: the map in the for-each loop is not mutated in both the method calls, only the information is used by them.

How can I make the above code run async? There are two methods being called getCourse(map, fee) and getInfoMap(map) and it takes quite a time to run them sequentially.

Answer 1

    // start parallel operations
    List<Future<Course>> coursesFut = Lists.newArrayList();
    Map<String, Future<Map<String, Student>>> resultsFut = Maps.newHashMap();
    for (Map<String, Object> map : jsonObjec t){
        coursesFut.add(CompletableFuture.supplyAsync(() -> getCourse(map, fee)));
        resultsFut.put(map.get(GROUP), CompletableFuture.supplyAsync(() -> getInfoMap(map)));
    }

    // collect results
    List<Course> courses = Lists.newArrayList();
    Map<String, Map<String, Student>> result = Maps.newHashMap();
    for (Future<Course> cf : coursesFut) {
        courses.add(cf.get());
    }
    for (Map.Entry<String, Future<Map<String, Student>> entry : resultsFut.entrySet()) {
        result.put(entry.getKey(), entry.getValue().get());
    }