在 ConcurrentMap 中填充条目<string, completablefuture<object> &gt; 在 java</string,>

Question

I am starting with the concept of CompletableFuture in java. I have a use case where I need to populate a values in Map<String, CompletableFuture<Object>> .

Assuming there is a Student entity class and a ConcurrentMap<String, CompletableFuture<Student>> . I tried to populate student entries into the map in following way:

Student student = new Student();
ConcurrentMap<String, CompletableFuture<Student>> studentMap = new ConcurrentMap<>();

CompletableFuture<Student> studentcf = new CompletableFuture<>();
studentcf.complete(student); // Not sure whether it is the right way to convert a entity into CompletableFuture

studentMap.put("Alex", studentcf);

The above solution worked but I am not sure whether it is the right way to do this (converting the entity to CompletableFuture). Can someone please suggest me the right way to do the above scenario?

Any suggestions will be helpful!! Thanks in advance!!

Answer 1

The above code is possible, but it doesn't make much sense. CompletableFuture is used for asynchronous calls. When the result of an operation is not known immediately, but only after some time.

Example:

    public Future<Student> calculateAsync() throws InterruptedException {
        CompletableFuture<Student> completableFuture 
          = new CompletableFuture<>();
     
        Executors.newCachedThreadPool().submit(() -> {
            Thread.sleep(5000);
            Student student = new Student();
            completableFuture.complete(student); //completed after 5 seconds
            return null;
        });
     
        return completableFuture; //return immediately
    }
    
    Future<Student> completableFuture = calculateAsync();
     
    // ... 
     
    Student result = completableFuture.get(); //This call is blocked until the result, which is generated by the embedded thread, is known.