How to sort String[] in List by timestamp?

Question

List<String[]> data = Importer.readCsv("test.csv");

A String[] item looks like this:

1. Position: name (String)
2. Position: 2017-03-14 18:22:44.149 (String)

What is a good approach in order to sort the list by the timestamp descending? I search for a solution without creating new Objects.

Answer 1

Use Collection.sort() and Comparator.comparing(), I find those easy to read when coming back to it later:

data.sort(Comparator.comparing((String[] o) -> o[1]).reversed());

You can compare the timestamp without conversion, as the format is "correctly" ordering the fields.

---

If you are confined to Java 7, there will be more boilerplate:

Collections.sort(data, new Comparator<String[]>()
{
    @Override
    public int compare(String[] o1, String[] o2)
    {
        return o2[1].compareTo(o1[1]);
        // return -o1[1].compareTo(o2[1]);
    }
});

Note that I need to compare o2 to o1 in this order or negate the result of comparing o1 to o2 to order the data descending. This becomes much more obvious in the first approach.