假设您有一个包含某些逻辑Stream的flatMap操作，您希望在Stream#empty满足某些条件时进行调用

listOfLists.stream().flatMap(list -> {
    // complex business logic, maybe even extracted in another method
    return xxx ? someList.stream() : Stream.empty();
});

另一个例子是，就像Optional<T>在方法返回的情况下使返回更安全Stream<T>（假设是工厂方法）

public <T> Stream<T> makeFooStreamFrom(Object... parameters) {
    // decide on what to do based on the parameters
    return decisionMadeToReturnAnEmptyStream ? Stream.empty() : Stream.of(foo, bar);
} 

至于方法接受Stream参数的例子，可以像这样给出一个很好的例子

public <T> void consumeStream(@NotNull Stream<T> stream) {
    // In this example, if this stream is null, you'll get a NullPointerException
    // However, if you make sure to invoke this method using Stream#empty
    // No need to worry about it
    // This is the security that Stream#empty will provide in this case
    stream.map(...).filter(...).forEach(...);
}

@daniu 带来的第四个例子是当你有一个 nullable 时List。这在java-9之前最相关，正如java-9引入的那样Stream#ofNullable，顺便说一句，它Stream#empty也在内部使用

这是它的实现，也是第四个例子

public static<T> Stream<T> ofNullable(T t) {
    return t == null ? Stream.empty()
                     : StreamSupport.stream(new Streams.StreamBuilderImpl<>(t), false);
}

我们会认为上面的示例并不相关，因为它Stream无论如何都会返回 a ，但是底层实现使用了一个EMPTY_SPLITERATOR内部命名的常量，这将有助于提高性能，因为它是可重用的。

• Note that `flatMap` explicitly allows the function to return `null` instead of `Stream.empty()`, to be treated the same. But people may prefer `Stream.empty()` as a matter of coding style. Further, you should not have “a nullable `List`”. Use an empty list instead. But, of course, `Collections.emptyList().stream()` also has to return a value, and it will be `Stream.empty()` in most implementations…