Question

I have a question about sorting.

    int[][] array = {{4,2},{1,7},{4,5},{1,2},{1,1},{4,1}};

After sorting this array, it will become like following.

    int[][] array = {{1,1},{1,2},{1,7},{4,1},{4,2},{4,5}};

I fell confused about that, if I perform a sort on rows at first and perform a sort on columns at second, how could I change two of the value in the same time when I sort rows and columns.

Answer 1

see this example…

Sort a two dimensional array based on one column
The first column is a date of format "yyyy.MM.dd HH:mm" and the second column is a String.

Since you say 2-D array, I assume “date of format …” means a String. Here’s code for sorting a 2-D array of String[][]:

import java.util.Arrays;
import java.util.Comparator;

public class Asdf {

public static void main(final String[] args) {
    final String[][] data = new String[][] {
            new String[] { "2009.07.25 20:24", "Message A" },
            new String[] { "2009.07.25 20:17", "Message G" },
            new String[] { "2009.07.25 20:25", "Message B" },
            new String[] { "2009.07.25 20:30", "Message D" },
            new String[] { "2009.07.25 20:01", "Message F" },
            new String[] { "2009.07.25 21:08", "Message E" },
            new String[] { "2009.07.25 19:54", "Message R" } };

    Arrays.sort(data, new Comparator<String[]>() {
        @Override
        public int compare(final String[] entry1, final String[] entry2) {
            final String time1 = entry1[0];
            final String time2 = entry2[0];
            return time1.compareTo(time2);
        }
    });

    for (final String[] s : data) {
        System.out.println(s[0] + " " + s[1]);
    }
}

}