private final boolean isDigit(char ch)
    {
        return ((ch >= 48) && (ch <= 57));
    }
This is an updated version with enhancements made by Daniel Migowski,
Andre Bogus, and David Koelle. Updated by David Koelle in 2017.

To use this class:
  Use the static "sort" method from the java.util.Collections class:
  Collections.sort(your list, new AlphanumComparator());
core/src/com/ray3k/skincomposer/utils/AlphanumComparator.java