How to use regex to get file extension? [duplicate]

Answer 1

Regex to capture file extension is:

(\\.[^.]+)$

Note that dot needs to be escaped to match a literal dot. However [^.] is a character class with negation that doesn't require any escaping since dot is treated literally inside [ and ].

\\.        # match a literal dot
[^.]+      # match 1 or more of any character but dot
(\\.[^.]+) # capture above test in group #1
$          # anchor to match end of input

Answer 2

You could use String class split() function. Here you could pass a regular expression. In this case, it would be "\.". This will split the string in two parts the second part will give you the file extension.

public class Sample{
  public static void main(String arg[]){
    String filename= "c:\\abc.txt";

    String fileArray[]=filename.split("\\.");

    System.out.println(fileArray[fileArray.length-1]); //Will print the file extension
  }
}

Answer 3

If you don't want to use RegEx you can go with something like this:

String fileString = "..." //this is your String representing the File
int lastDot = fileString.lastIndexOf('.');
String extension = fileString.subString(lastDot+1);