diagonal, Java - rextester

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//'main' method must be in a class 'Rextester'.
//openjdk version '11.0.5'

import java.util.*;
import java.lang.*;

class Rextester
{  
  static ArrayList<String>  imprimirDiagonalDesc(char matriz[][]){
      ArrayList<String> list = new ArrayList<>(); 
      String aux="";
      int d = matriz.length;
      for (int i = d-1; i>=0; i--) {
        int col = i, row = 0;
      while (col < d && row < d) {
         aux+=String.valueOf(matriz[col][row]);
         col++;
         row++;
      }
      list.add(aux);
      aux="";
      }
      for (int j = 0; j < d-1; j++) {
            int row = 0, col = j+1;
                while (row < d && col <d) {
                aux+=String.valueOf(matriz[row][col]);
                col++;
                row++;
            }
            list.add(aux);
            aux="";
        }
        return list;
    }
      
    public static void main(String args[])
    {
      char[][] matriz =   {{'p', 'a', 'r', 'p', 'a', 'd', 'o'},
                           {'t', 'i', 'j', 'e', 'r', 'a', 's'},
                           {'f', 'e', 'l', 'p', 'u', 'd', 'o'},
                           {'c', 'a', 'r', 'a', 'c', 'o', 'l'},
                           {'o', 'm', 'i', 'c', 'r', 'o', 'n'},
                           {'b', 'a', 't', 'a', 'l', 'l', 'a'},
                           {'z', 'a', 'r', 'p', 'a', 'z', 'o'},
            };
 
 
 System.out.println(imprimirDiagonalDesc(matriz));
        
        
        
        
    }
}

[ + ] Show input
Compilation time: 0.82 sec, absolute running time: 0.23 sec, cpu time: 0.21 sec, memory peak: 38 Mb, absolute service time: 1,18 sec