Is there a better way to get file basename and extension than something like
File f = ...
String name = f.getName();
int dot = name.lastIndexOf('.');
String base = (dot == -1) ? name : name.substring(0, dot);
String extension = (dot == -1) ? "" : name.substring(dot+1);
I know others have mentioned String.split
, but here is a variant that only yields two tokens (the base and the extension):
String[] tokens = fileName.split("\\.(?=[^\\.]+$)");
For example:
"test.cool.awesome.txt".split("\\.(?=[^\\.]+$)");
Yields:
["test.cool.awesome", "txt"]
The regular expression tells Java to split on any period that is followed by any number of non-periods, followed by the end of input. There is only one period that matches this definition (namely, the last period).
Technically Regexically speaking, this technique is called zero-width positive lookahead.
BTW, if you want to split a path and get the full filename including but not limited to the dot extension, using a path with forward slashes,
String[] tokens = dir.split(".+?/(?=[^/]+$)");
For example:
String dir = "/foo/bar/bam/boozled";
String[] tokens = dir.split(".+?/(?=[^/]+$)");
// [ "/foo/bar/bam/" "boozled" ]
What's wrong with your code? Wrapped in a neat utility method it's fine.
What's more important is what to use as separator — the first or last dot. The first is bad for file names like "setup-2.5.1.exe", the last is bad for file names with multiple extensions like "mybundle.tar.gz".
You can also user java Regular Expression. String.split() also uses the expression internally. Refer http://download.oracle.com/javase/1.4.2/docs/api/java/util/regex/Pattern.html
http://docs.oracle.com/javase/6/docs/api/java/io/File.html#getName()
From http://www.xinotes.org/notes/note/774/ :
Java has built-in functions to get the basename and dirname for a given file path, but the function names are not so self-apparent.
import java.io.File;
public class JavaFileDirNameBaseName {
public static void main(String[] args) {
File theFile = new File("../foo/bar/baz.txt");
System.out.println("Dirname: " + theFile.getParent());
System.out.println("Basename: " + theFile.getName());
}
}
And there exists no reliable function for it. Consider for example this filename:
archive.tar.gz
What is the extension? DOS users would have preferred the name archive.tgz
. Sometimes you see stupid Windows applications that first decompress the file (yielding a .tar
file), then you have to open it again to see the archive contents.
In this case, a more reasonable notion of file extension would have been .tar.gz
. There are also .tar.bz2
, .tar.xz
, .tar.lz
and .tar.lzma
file "extensions" in use. But how would you decide, whether to split at the last dot, or the second-to-last dot?
The Java 7 function Files.probeContentType will likely be much more reliable to detect file types than trusting the file extension. Pretty much all the Unix/Linux world as well as your Webbrowser and Smartphone already does it this way.
Old question but I usually use this solution:
import org.apache.commons.io.FilenameUtils;
String fileName = "/abc/defg/file.txt";
String basename = FilenameUtils.getBaseName(fileName);
String extension = FilenameUtils.getExtension(fileName);
System.out.println(basename); // file
System.out.println(extension); // txt (NOT ".txt" !)
Source: http://www.java2s.com/Code/Java/File-Input-Output/Getextensionpathandfilename.htm
such an utility class :
class Filename {
private String fullPath;
private char pathSeparator, extensionSeparator;
public Filename(String str, char sep, char ext) {
fullPath = str;
pathSeparator = sep;
extensionSeparator = ext;
}
public String extension() {
int dot = fullPath.lastIndexOf(extensionSeparator);
return fullPath.substring(dot + 1);
}
public String filename() { // gets filename without extension
int dot = fullPath.lastIndexOf(extensionSeparator);
int sep = fullPath.lastIndexOf(pathSeparator);
return fullPath.substring(sep + 1, dot);
}
public String path() {
int sep = fullPath.lastIndexOf(pathSeparator);
return fullPath.substring(0, sep);
}
}
usage:
public class FilenameDemo {
public static void main(String[] args) {
final String FPATH = "/home/mem/index.html";
Filename myHomePage = new Filename(FPATH, '/', '.');
System.out.println("Extension = " + myHomePage.extension());
System.out.println("Filename = " + myHomePage.filename());
System.out.println("Path = " + myHomePage.path());
}
}
Maybe you could use String#split
To answer your comment:
I'm not sure if there can be more than one . in a filename, but whatever, even if there are more dots you can use the split. Consider e.g. that:
String input = "boo.and.foo";
String[] result = input.split(".");
This will return an array containing:
{ "boo", "and", "foo" }
So you will know that the last index in the array is the extension and all others are the base.
Source: Stackoverflow.com