public static String getExtension(String filename) {
        if (filename == null) {
            return null;
        }
        int index = indexOfExtension(filename);
        if (index == -1) {
            return "";
        } else {
            return filename.substring(index + 1);
        }
    }
public static String getExtension(String filename) {
        if (filename == null) {
            return null;
        }
        int index = indexOfExtension(filename);
        if (index == -1) {
            return "";
        } else {
            return filename.substring(index + 1);
        }
    }
public static String getExtension ( String filename ) { if ( filename == null ) { return null ; } int index = indexOfExtension ( filename ) ; if ( index == - 1 ) { return "" ; } else { return filename . substring ( index + 1 ) ; } }
Gets the extension of a filename.
<p>
This method returns the textual part of the filename after the last dot.
There must be no directory separator after the dot.
<pre>
foo.txt      --> "txt"
a/b/c.jpg    --> "jpg"
a/b.txt/c    --> ""
a/b/c        --> ""
</pre>
<p>
The output will be the same irrespective of the machine that the code is running on.

@param filename the filename to retrieve the extension of.
@return the extension of the file or an empty string if none exists.
Gets the extension of a filename . <p > This method returns the textual part of the filename after the last dot . There must be no directory separator after the dot . <pre > foo . txt -- > txt a / b / c . jpg -- > jpg a / b . txt / c -- > a / b / c -- > < / pre > <p > The output will be the same irrespective of the machine that the code is running on .