Question

I have an array of filenames and need to sort that array by the extensions of the filename. Is there an easy way to do this?

Answer 1

Arrays.sort(filenames, new Comparator<String>() {     @Override     public int compare(String s1, String s2) {         // the +1 is to avoid including the '.' in the extension and to avoid exceptions         // EDIT:         // We first need to make sure that either both files or neither file         // has an extension (otherwise we'll end up comparing the extension of one         // to the start of the other, or else throwing an exception)         final int s1Dot = s1.lastIndexOf('.');         final int s2Dot = s2.lastIndexOf('.');         if ((s1Dot == -1) == (s2Dot == -1)) { // both or neither             s1 = s1.substring(s1Dot + 1);             s2 = s2.substring(s2Dot + 1);             return s1.compareTo(s2);         } else if (s1Dot == -1) { // only s2 has an extension, so s1 goes first             return -1;         } else { // only s1 has an extension, so s1 goes second             return 1;         }     } }); 

For completeness: java.util.Arrays and java.util.Comparator.