空源FilterInputStream中的/ FilterOutputStream中的

问题描述

我在写类的工作就像。

看起来

公共FilterReadableByteChannel实现的ReadableByteChannel {    //我应该允许空通道？
    公共FilterReadableByteChannel（最终的ReadableByteChannel通道）{
       // ...
    }
}


和我发现，无论和许可证空来源。

  *参数的基本输入流中，或LT; code＆GT;空＆LT; / code＆GT;如果
 *该实例是没有基础流被创建。
 

问：

1. 对此有任何实际的原因是什么？


2. 有没有改变底层源创建后的任何可能的情况下？

我知道为什么不呢？可能是一个答案，但我想知道，如果有，为什么原来的API设计这样做的任何理由。

解决方案

Yes. Even if not declared as such, classes Filter*Stream are conceptually abstract classes. IOW, they only exist to be extended. Subclasses could need to provide the in or out parameters after construction (example: lazily; on first real use), and Filter*Stream gives them this flexibility.

The obvious case is when source is initially null. Other cases that come to my mind are: 1. Creating a subclass of Filter*Stream that acts as a selector. IOW, has several underlying streams and methods to switch from one to the other. 2. Creating a subclass of FilterInputStream that concatenates different InputStreams. 3. Creating a subclass of FilterOutputStream that splits output into different OutputStreams.

Yes: generality.

这篇关于空源FilterInputStream中的/ FilterOutputStream中的的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！