获取Java InputStream后面文件的字节数 [英] Get the number of bytes of a file behind a Java InputStream

问题描述

正如标题所述，我需要知道在InputStream后面的文件有多少字节。
我不想下载所有字节和计数（需要很长的时间）。我只需要知道文件有多少字节即可。

As the title says, I need to know how many bytes the file has that's "behind" an InputStream. I don't want to download all bytes and count (takes to long). I just need to know how many bytes the file has.

就像这样：

int numberOfBytes = countBytes(inputStream);

所以，我需要一个countBytes（InputStream inputStream）的实现

So, I need an implementation for countBytes(InputStream inputStream)

推荐答案

除了消耗整个流并计算字节数之外，您不能（没有API）。

Other than by consuming the entire stream and counting the bytes, you can't (there's no API for it).

有 available（）方法，但它显然没有按照您的要求进行操作：

There's the available() method, but it quite explicitly doesn't do what you're asking:

请注意，尽管某些InputStream实现将返回流中的字节总数，但许多不会。

如果 InputStream 与文件（而不是套接字）相关联，也许您可​​以使用其他要获取其大小的API？

If the InputStream is associated with a file (and not, say, a socket), perhaps you could use a different API to get its size?

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