正则表达式从路径获取带或不带扩展名的文件名

Question

Looking for a regex to extract out the filename part excluding the extension from a path in this code

String filename = fullpath.replaceFirst(regex, "$1")

eg for starter, here is the most simple case and what I have done:

• /path/filename.ext -> filename ( fullpath.replaceFirst(".*/(.*)\\..*", "$1") )

Here are some more advance cases that I need help with:

• /filename.ext -> filename (can start with /)
• filename. -> filename (can end with.)
• /filename -> filename (can have no.)
• filename.ext -> filename (can have no /)
• filename -> filename (can have no. and /)
• .filename ->.filename (can start with.)
• /path/.filename ->.filename (can start with. right after /)
• filename.part1.ext -> filename.part1 (can have middle.)
• /path_a/path.b/ -> (empty string) (can have no filename)
• /path_a/path.b/filename -> filename (can have. in path before /)

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Edited: There is no actual file here and the fullpath does not lead to any file. It is coming from a URL request.

Answer 1

The following regex will match desired parts:

^(?:.*\/)?([^\/]+?|)(?=(?:\.[^\/.]*)?$)

Explanation:

• ^ Match start of the line
• (?: Start of a non-capturing group
  • .*\/ Match up to last / character
• )? End of the non-capturing (optional)
• ([^\/]+?|) Capture anything but / ungreedily or nothing
• (?= Start of a positive lookahead
  • (?:\.[^\/.]*)? Match an extension (optional)
  • $ Assert end of the line
• ) End of the positive lookahead

but if you are dealing with a multi-line input string and need a bit faster regex try this one instead (with m flag on):

^(?:[^\/\r\n]*\/)*([^\/\r\n]+?|)(?=(?:\.[^\/\r\n.]*)?$)

See live demo here

Filename would be captured in the first capturing group.

Answer 2

You can use the getName() function on a File object and then remove the extension using a Regex and you can check if it's a file too:

File file = new File(fullpath);
if (file.isFile()) return file.getName().replace("\..*", "");
else return "";

Answer 3

Use the path file (String pathFile) to get the name file with extension and remove it with FilenameUtils.removeExtension

String nameDocument = pathFile.substring(pathFile.lastIndexOf("/") + 1);

String fileNameWithOutExt = FilenameUtils.removeExtension(nameDocument);