Sorting ArrayList by objects inside (String, Date, etc.) in reverse order

Question

Assume that there is an ArrayList<Object[]> containing various objects inside:

ArrayList<Object[]> list = new ArrayList<>();
list.add(new Object[]{"cat", (long)1422355945});
list.add(new Object[]{"dog", (long)1422355970});
list.add(new Object[]{"rat", (long)1422355900});

How can we sort this list effectively by first Object (which is String) in reverse order? And to do the same by second Object (which is long)?

Yes, I expected this answer. Could we share real examples here? — Ernestas Gruodis, Jan 27 '15 at 10:59

score 1 · Accepted Answer · edited Jan 27 '15 at 11:13

1

Just create a Comparator, similar to the example below:

    List<Object[]> list = new ArrayList<>();
    list.add(new Object[] { "cat", (long) 1422355945 });
    list.add(new Object[] { "dog", (long) 1422355970 });
    list.add(new Object[] { "rat", (long) 1422355900 });

    Collections.sort(list, new Comparator<Object[]>() {
        @Override
        public int compare(Object[] o1, Object[] o2) {
            int cmp1 = ((String) o1[0]).compareTo((String) o2[0]);
            if (cmp1 == 0) {
                return Long.compare((Long) o1[1], (Long) o2[1]);
            }
            return cmp1;
        }
    });

edited Jan 27 '15 at 11:13

Ernestas Gruodis

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answered Jan 27 '15 at 11:04

nogard

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How can we do that in reverse order (just by one column)? – Ernestas Gruodis Jan 27 '15 at 11:29
1

@ErnestasGruodis For that column, compare o2 with o1, instead of o1 with o2. – Florent Bayle Jan 27 '15 at 11:32

Sorting ArrayList by objects inside (String, Date, etc.) in reverse order

1 Answers1