Question

How to flatten a 2D array into a sorted one-dimensional array with unique values in Java

Answer 1

import java.util.Set;
import java.util.Arrays;
import java.util.Comparator;
import java.util.stream.Collectors;

public class Flatten2DArrayIntoASorted1DArrayWithUniqueValues_Java {
    public static void main(String[] args) {
        int[][] array2d = {
            {4, 3, 3, 2},
            {30, 10},
            {10},
            {1, 1, 6, 7, 7, 7, 8},
        };

        Set<Integer> set = Arrays.stream(array2d)
                                  .flatMapToInt(Arrays::stream)
                                  .distinct()
                                  .boxed()
                                  .sorted(Comparator.naturalOrder())
                                  .collect(Collectors.toSet());

        System.out.println(set.stream().map(String::valueOf).collect(Collectors.joining(", ")));
        
        for (Integer n : set) {
            System.out.print(n + " ");
        }
    }
}



/*
run:

1, 2, 3, 4, 6, 7, 8, 10, 30
1 2 3 4 6 7 8 10 30 

*/

 

70+ SQL courses for beginners and professionals