Use of futures may be implicit (any use of the future automatically obtains its value, as if it were an ordinary reference) or explicit (the user must call a function to obtain the value, such as the get method of java.util.concurrent.Future or java.util.concurrent.CompletableFuture in Java).
对future的使用可能是隐式的（任何对future的使用都会自动获得它的值，它就像是普通的引用一样）或显式的（用户必须调用函数来获取值，例如Java中的java.util.concurrent.Future或java.util.concurrent.CompletableFuture的get方法）。