Question

2) Given an array of two-dimensional numbers. This array is arranged in a lexical order (first by the first digits of the number, then the second digits of these numbers are compared when they have the same value).

Answer 1

Arrays.sort(source, Arrays::compare); 
nt[][] sorted = Arrays.stream(source)
                       .sorted(Arrays::compare)
                       .toArray(int[][]::new);