extract the extension of a file

[skarosi]

Hi all,
i am using fileChooser to find a file and save the address to a String. how can i get just the extension of the file?
i tried with a conjuction of subString and indexOf, but if there are more than one '.' on the address i get the wrong substring. obviously i cant just say
subString(length-4,length);
cos for files with more than 3 characters on the extensions, such as *.java, will not work.
any help?
also, is it possible to set the home directory on the fileChooser window? it always opens on the "my documents" directory (for windows at least) even though the file is on a subfolder

cheers

 

[sedj]

One way to get a file extenstion purely from the name of the file would be like this :

	String filename = "abc.txt";
	String[] parts = filename.split("\\.");
	String ext;

	if (parts.length < 2) {
		ext = filename;
	} else {
		ext = parts[parts.length -1];
	}
	System.out.println(ext);

This would also work if you had "abc.tmp.txt" etc.

--------------------------------------------------
Free Database Connection Pooling Software

http://www.primrose.org.uk

 

[skarosi]

thanks man, this did just the trick.
so split is splitting the string to substrings between the character u want. thats cool, never new that command
thanks again

 

[Diancecht]

Be careful.

In a file with no extension, that will return the name of the file.

Cheers,

Dian

 

[tom62]

Another way to do it, could be:

public String getExtension(String fileName) {
int i = fileName.lastIndexOf(".") + 1;
return i == 0 ? "" : fileName.substring(i);
}

Ciao,

Tom

 

[ishnid]

If indexOf was giving you the wrong dot, you could use lastIndexOf instead, to get the position of the last dot in the filename.

 

[skarosi]

thanks for the heads up Diancecht. i fixed that now, if the file has no extension i set it to " ", so it is blank.#

i didnt know that lastIndexOf existed, now i already made it the other way. thanks though. it was great help

 

[ishnid]

It's well worth having a quick look through the API Documentation whenever you've some free time - particularly for classes you'll be using frequently (like String). Even if you don't need the methods now, it's good to know what's available to you later on.

 

[skarosi]

i know the API and have used it frequently over the years.
it is just that i havent looked on all the methods or classes.