How do I trim a file extension from a String in Java?

This is the sort of code that we shouldn't be doing ourselves. Use libraries for the mundane stuff, save your brain for the hard stuff.

In this case, I recommend using FilenameUtils.removeExtension() from Apache Commons IO

str.substring(0, str.lastIndexOf('.'))

As using the String.substring and String.lastIndex in a one-liner is good, there are some issues in terms of being able to cope with certain file paths.

Take for example the following path:

a.b/c

Using the one-liner will result in:

a

That's incorrect.

The result should have been c, but since the file lacked an extension, but the path had a directory with a . in the name, the one-liner method was tricked into giving part of the path as the filename, which is not correct.

Need for checks

Inspired by skaffman's answer, I took a look at the FilenameUtils.removeExtension method of the Apache Commons IO.

In order to recreate its behavior, I wrote a few tests the new method should fulfill, which are the following:

Path                  Filename
--------------        --------
a/b/c                 c
a/b/c.jpg             c
a/b/c.jpg.jpg         c.jpg

a.b/c                 c
a.b/c.jpg             c
a.b/c.jpg.jpg         c.jpg

c                     c
c.jpg                 c
c.jpg.jpg             c.jpg

(And that's all I've checked for -- there probably are other checks that should be in place that I've overlooked.)

The implementation

The following is my implementation for the removeExtension method:

public static String removeExtension(String s) {

    String separator = System.getProperty("file.separator");
    String filename;

    // Remove the path upto the filename.
    int lastSeparatorIndex = s.lastIndexOf(separator);
    if (lastSeparatorIndex == -1) {
        filename = s;
    } else {
        filename = s.substring(lastSeparatorIndex + 1);
    }

    // Remove the extension.
    int extensionIndex = filename.lastIndexOf(".");
    if (extensionIndex == -1)
        return filename;

    return filename.substring(0, extensionIndex);
}

Running this removeExtension method with the above tests yield the results listed above.

The method was tested with the following code. As this was run on Windows, the path separator is a \ which must be escaped with a \ when used as part of a String literal.

System.out.println(removeExtension("a\\b\\c"));
System.out.println(removeExtension("a\\b\\c.jpg"));
System.out.println(removeExtension("a\\b\\c.jpg.jpg"));

System.out.println(removeExtension("a.b\\c"));
System.out.println(removeExtension("a.b\\c.jpg"));
System.out.println(removeExtension("a.b\\c.jpg.jpg"));

System.out.println(removeExtension("c"));
System.out.println(removeExtension("c.jpg"));
System.out.println(removeExtension("c.jpg.jpg"));

The results were:

c
c
c.jpg
c
c
c.jpg
c
c
c.jpg

The results are the desired results outlined in the test the method should fulfill.

String foo = "title part1.txt";
foo = foo.substring(0, foo.lastIndexOf('.'));

Use a method in com.google.common.io.Files class if your project is already dependent on Google core library. The method you need is getNameWithoutExtension.

you can try this function , very basic

public String getWithoutExtension(String fileFullPath){
    return fileFullPath.substring(0, fileFullPath.lastIndexOf('.'));
}

String fileName="foo.bar";
int dotIndex=fileName.lastIndexOf('.');
if(dotIndex>=0) { // to prevent exception if there is no dot
  fileName=fileName.substring(0,dotIndex);
}

Is this a trick question? :p

I can't think of a faster way atm.

I found coolbird's answer particularly useful.

But I changed the last result statements to:

if (extensionIndex == -1)
  return s;

return s.substring(0, lastSeparatorIndex+1) 
         + filename.substring(0, extensionIndex);

as I wanted the full path name to be returned.

So "C:\Users\mroh004.COM\Documents\Test\Test.xml" becomes 
   "C:\Users\mroh004.COM\Documents\Test\Test" and not
   "Test"

Use a regex. This one replaces the last dot, and everything after it.

String baseName = fileName.replaceAll("\\.[^.]*$", "");

You can also create a Pattern object if you want to precompile the regex.

If you use Spring you could use

org.springframework.util.StringUtils.stripFilenameExtension(String path)

Strip the filename extension from the given Java resource path, e.g.

"mypath/myfile.txt" -> "mypath/myfile".

Params: path – the file path

Returns: the path with stripped filename extension

String[] splitted = fileName.split(".");
String fileNameWithoutExtension = fileName.replace("." + splitted[splitted.length - 1], "");

The best what I can write trying to stick to the Path class:

Path removeExtension(Path path) {
    return path.resolveSibling(path.getFileName().toString().replaceFirst("\\.[^.]*$", ""));
}

dont do stress on mind guys. i did already many times. just copy paste this public static method in your staticUtils library for future uses ;-)

static String removeExtension(String path){
        String filename;
        String foldrpath;
        String filenameWithoutExtension;
        if(path.equals("")){return "";}
        if(path.contains("\\")){    // direct substring method give wrong result for "a.b.c.d\e.f.g\supersu"
            filename = path.substring(path.lastIndexOf("\\"));
            foldrpath = path.substring(0, path.lastIndexOf('\\'));;
            if(filename.contains(".")){
                filenameWithoutExtension = filename.substring(0, filename.lastIndexOf('.'));
            }else{
                filenameWithoutExtension = filename;
            }
            return foldrpath + filenameWithoutExtension;
        }else{
            return path.substring(0, path.lastIndexOf('.'));
        }
    }

I would do like this:

String title_part = "title part1.txt";
int i;
for(i=title_part.length()-1 ; i>=0 && title_part.charAt(i)!='.' ; i--);
title_part = title_part.substring(0,i);

Starting to the end till the '.' then call substring.

Edit: Might not be a golf but it's effective :)

String img = "example.jpg";
// String imgLink = "http://www.example.com/example.jpg";
URI uri = null;

try {
    uri = new URI(img);
    String[] segments = uri.getPath().split("/");
    System.out.println(segments[segments.length-1].split("\\.")[0]);
} catch (Exception e) {
    e.printStackTrace();
}

This will output example for both img and imgLink

private String trimFileName(String fileName)
    {
        String[] ext;
        ext = fileName.split("\\.");
        
        return fileName.replace(ext[ext.length - 1], "");

    }

This code will spilt the file name into parts where ever it has " . ", For eg. If the file name is file-name.hello.txt then it will be spilted into string array as , { "file-name", "hello", "txt" }. So anyhow the last element in this string array will be the file extension of that particular file , so we can simply find the last element of any arrays with arrayname.length - 1, so after we get to know the last element, we can just replace the file extension with an empty string in that file name. Finally this will return file-name.hello. , if you want to remove also the last period then you can add the string with only period to the last element of string array in the return line. Which should look like,

return fileName.replace("." +  ext[ext.length - 1], "");

public static String removeExtension(String file) {
    if(file != null && file.length() > 0) {
        while(file.contains(".")) {
            file = file.substring(0, file.lastIndexOf('.'));
        }
    }
    return file;
}