question: public boolean matches ( String filename ) { if ( exts == null ) return true ; int j = filename . lastIndexOf ( "." ) ; if ( j == - 1 || j == filename . length ( ) ) return false ; String suffix = filename . substring ( j + 1 ) ; return exts . contains ( suffix ) ; }
target:  Returns true if a file with the given name is of this media type, i.e., the suffix of the filename matches one of this' extensions. 