实用方法 - 传递文件或字符串？ [英] Utility method - Pass a File or String?

问题描述

以下是实用程序方法的示例：

Here's an example of a utility method:

public static Long getFileSize(String fileString) {

    File file = new File(fileString);

    if (file == null || !file.isFile())
        return null;

    return file.length();
}

将String而不是File传递给方法是一种好习惯像这样？一般来说，在制作这种风格的实用方法时应该采用什么推理？

Is it a good practise to pass a String rather than a File to a method like this? In general what reasoning should be applied when making utility methods of this style?

推荐答案

这是我的首选解决方案：

This is my preferred solution:

public static Long getFileSize(String path) {
    return getFileSize(new File(path));
}

public static Long getFileSize(File file) {
    return (!file.isFile()) ? -1L : file.length();
}

注意它返回-1L而不是0L，以允许调用者区分空文件和由于某种原因无法确定长度的文件。在没有长度文件的情况下， file.length（）将返回零;例如

Note that it is returning -1L rather than 0L, to allow the caller to distinguish between an empty file, and a "file" whose length cannot be determined for some reason. The file.length() will return zero in some cases where you don't have a zero length file; e.g.

• 当文件不存在时


• 当文件是一个目录


• 当文件是一个特殊的文件（例如设备文件，管道等），操作系统无法确定其长度。

• when the file does not exist
• when the file is a directory
• when the file is a special file (e.g. device file, pipe, etc) and the OS cannot determine its length.

file.isFile（）调用处理这些情况。但是，方法是否应该返回 -1L 或抛出异常是有争议的。这场辩论的答案取决于 -1L 案例是正常还是例外，而这只能参考该方法的上下文来确定。旨在使用，

The file.isFile() call deals with these cases. However, it is debatable whether the method(s) should return -1L or throw an exception. The answer to this debate turns on whether the -1L cases are "normal" or "exceptional", and that can only be determined with reference to the contexts in which the method is designed to be used,

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