Java sort array by the third element

Question

i want to sort a String array descendant by it's third column in descend, the problem is that i want to sort by it's numeric value.

Example:

If i have this array initially:

String [][] array = new String[][] {
  {"Barcelona", "156", "1604"}, 
  {"Girona", "256", "97"},
  {"Tarragona", "91", "132"},
  {"Saragossa", "140", "666"}
}

I want it to become this:

{
  {"Barcelona", "156", "1604"}, 
  {"Saragossa", "140", "666"}, 
  {"Tarragona", "91", "132"}, 
  {"Girona", "256", "97"}
}

How can i do that?

Perhaps draw inspiration from stackoverflow.com/questions/5805602/… — Eli Sadoff
– Eli Sadoff, Commented Jan 11, 2017 at 21:40
Arrays.sort(array, Comparator.comparingInt((String[] a) -> Integer.parseInt(a[2])).reversed()); — shmosel
– shmosel, Commented Jan 11, 2017 at 21:42

Juraj · Accepted Answer · 2017-01-11 21:57:50Z

5

Sort by asc:

Arrays.sort(array, Comparator.comparingInt(a -> Integer.valueOf(a[2])));

Sort by desc:

Arrays.sort(array, Comparator.comparingInt(a -> Integer.valueOf(a[2])*-1)); 
// or this
Arrays.sort(array, Comparator.comparingInt((String[] a) -> Integer.valueOf(a[2])).reversed());

answered Jan 11, 2017 at 21:57

Juraj

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Elliott Frisch · Accepted Answer · 2017-01-11 23:25:07Z

4

You can implement a custom Comparator<String[]> to perform your comparisons. Something like,

String[][] array = new String[][] { { "Barcelona", "156", "1604" }, 
        { "Girona", "256", "97" }, { "Tarragona", "91", "132" }, 
        { "Saragossa", "140", "666" } };
Arrays.sort(array, new Comparator<String[]>() {
    @Override
    public int compare(String[] o1, String[] o2) {
        return Integer.valueOf(o2[2]).compareTo(Integer.valueOf(o1[2]));
    }
});
System.out.println(Arrays.deepToString(array));

Which outputs (as requested)

[[Barcelona, 156, 1604], [Saragossa, 140, 666], [Tarragona, 91, 132], [Girona, 256, 97]]

See also, Object Ordering - The Java Tutorials (and especially the subsection "Writing Your Own Comparable Types") for more.

edited Jan 11, 2017 at 23:25

answered Jan 11, 2017 at 21:44

Elliott Frisch

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1 Comment

user7274818 Over a year ago

The problem is that i don't know how to use Comparator, any good guide or video?

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