[java] Sort a two dimensional array based on one column

class ArrayComparator implements Comparator<Comparable[]> {
    private final int columnToSort;
    private final boolean ascending;

    public ArrayComparator(int columnToSort, boolean ascending) {
        this.columnToSort = columnToSort;
        this.ascending = ascending;
    }

    public int compare(Comparable[] c1, Comparable[] c2) {
        int cmp = c1[columnToSort].compareTo(c2[columnToSort]);
        return ascending ? cmp : -cmp;
    }
}

This way you can handle any type of data in those arrays (as long as they're Comparable) and you can sort any column in ascending or descending order.

String[][] data = getData();
Arrays.sort(data, new ArrayComparator(0, true));

PS: make sure you check for ArrayIndexOutOfBounds and others.

EDIT: The above solution would only be helpful if you are able to actually store a java.util.Date in the first column or if your date format allows you to use plain String comparison for those values. Otherwise, you need to convert that String to a Date, and you can achieve that using a callback interface (as a general solution). Here's an enhanced version:

class ArrayComparator implements Comparator<Object[]> {
    private static Converter DEFAULT_CONVERTER = new Converter() {
        @Override
        public Comparable convert(Object o) {
            // simply assume the object is Comparable
            return (Comparable) o;
        }
    };
    private final int columnToSort;
    private final boolean ascending;
    private final Converter converter;


    public ArrayComparator(int columnToSort, boolean ascending) {
        this(columnToSort, ascending, DEFAULT_CONVERTER);
    }

    public ArrayComparator(int columnToSort, boolean ascending, Converter converter) {
        this.columnToSort = columnToSort;
        this.ascending = ascending;
        this.converter = converter;
    }

    public int compare(Object[] o1, Object[] o2) {
        Comparable c1 = converter.convert(o1[columnToSort]);
        Comparable c2 = converter.convert(o2[columnToSort]);
        int cmp = c1.compareTo(c2);
        return ascending ? cmp : -cmp;
    }

}

interface Converter {
    Comparable convert(Object o);
}

class DateConverter implements Converter {
    private static final DateFormat df = new SimpleDateFormat("yyyy.MM.dd hh:mm");

    @Override
    public Comparable convert(Object o) {
        try {
            return df.parse(o.toString());
        } catch (ParseException e) {
            throw new IllegalArgumentException(e);
        }
    }
}

And at this point, you can sort on your first column with:

Arrays.sort(data, new ArrayComparator(0, true, new DateConverter());

I skipped the checks for nulls and other error handling issues.

I agree this is starting to look like a framework already. :)

Last (hopefully) edit: I only now realize that your date format allows you to use plain String comparison. If that is the case, you don't need the "enhanced version".