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

Question

What's the most efficient way to trim the suffix in Java, like this:

title part1.txt
title part2.html
=>
title part1
title part2

Answer 1

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

Answer 2

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

Answer 3

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.

Answer 4

BTW, in my case, when I wanted a quick solution to remove a specific extension, this is approximately what I did:

  if (filename.endsWith(ext))
    return filename.substring(0,filename.length() - ext.length());
  else
    return filename;

Answer 5

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

Answer 6

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.

Answer 7

you can try this function , very basic

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

Answer 8

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.

Answer 9

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"

Answer 10

filename.substring(filename.lastIndexOf('.'), filename.length()).toLowerCase();

Answer 11

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.

Answer 12

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

Answer 13

create a new file with string image path

String imagePath;
File test = new File(imagePath);
test.getName();
test.getPath();
getExtension(test.getName());


public static String getExtension(String uri) {
        if (uri == null) {
            return null;
        }

        int dot = uri.lastIndexOf(".");
        if (dot >= 0) {
            return uri.substring(dot);
        } else {
            // No extension.
            return "";
        }
    }

Answer 14

org.apache.commons.io.FilenameUtils version 2.4 gives the following answer

public static String removeExtension(String filename) {
    if (filename == null) {
        return null;
    }
    int index = indexOfExtension(filename);
    if (index == -1) {
        return filename;
    } else {
        return filename.substring(0, index);
    }
}

public static int indexOfExtension(String filename) {
    if (filename == null) {
        return -1;
    }
    int extensionPos = filename.lastIndexOf(EXTENSION_SEPARATOR);
    int lastSeparator = indexOfLastSeparator(filename);
    return lastSeparator > extensionPos ? -1 : extensionPos;
}

public static int indexOfLastSeparator(String filename) {
    if (filename == null) {
        return -1;
    }
    int lastUnixPos = filename.lastIndexOf(UNIX_SEPARATOR);
    int lastWindowsPos = filename.lastIndexOf(WINDOWS_SEPARATOR);
    return Math.max(lastUnixPos, lastWindowsPos);
}

public static final char EXTENSION_SEPARATOR = '.';
private static final char UNIX_SEPARATOR = '/';
private static final char WINDOWS_SEPARATOR = '\\';

Answer 15

 private String trimFileExtension(String fileName)
  {
     String[] splits = fileName.split( "\\." );
     return StringUtils.remove( fileName, "." + splits[splits.length - 1] );
  }

Answer 16

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

Answer 17

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 :)

Answer 18

Keeping in mind the scenarios where there is no file extension or there is more than one file extension

example Filename : file | file.txt | file.tar.bz2

/**
 *
 * @param fileName
 * @return file extension
 * example file.fastq.gz => fastq.gz
 */
private String extractFileExtension(String fileName) {
    String type = "undefined";
    if (FilenameUtils.indexOfExtension(fileName) != -1) {
        String fileBaseName = FilenameUtils.getBaseName(fileName);
        int indexOfExtension = -1;
        while (fileBaseName.contains(".")) {
            indexOfExtension = FilenameUtils.indexOfExtension(fileBaseName);
            fileBaseName = FilenameUtils.getBaseName(fileBaseName);
        }
        type = fileName.substring(indexOfExtension + 1, fileName.length());
    }
    return type;
}

Answer 19

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

Answer 20

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

Answer 21

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

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