Question

I have four arrays, each with 3 (but can be more) elements. I am trying to fill a 4 x aa.length*bb.length*cc.length*dd.length array with all possible combinations of each element. I am trying to do this with nested for loops, but my logic is faulty. I am not sure what the most efficient way to do this would be.
this is what my caffeine starved brain has come up with so far.

String[] AA={DDDD, HHHH, ZZZZ};
String[] BB={DDDD, HHHH, ZZZZ};
String[] CC={DDDD, HHHH, ZZZZ};
String[] DD={DDDD, HHHH, ZZZZ};


String[][] 2Darray = new String[4][AA.length*BB.length*CC.length*DD.length];

for (int i = 0; i <AA.length; i++){

  for (int j = 0; j < BB.length; j++){

    for (int k = 0; k < CC.length; k++){

      for (int L = 0; L < DD.length; L++){

        2Darray[3][i+j+k+L] = DD[L]; 
        2Darray[2][i+j+k] = CC[k];
        2Darray[1][i+j] = BB[j];
        2Darray[0][i] = AA[i];

      }
    }
  }
}

the printed output of this looks like:

DDDD DDDD DDDD DDDD
HHHH DDDD DDDD DDDD
ZZZZ DDDD DDDD DDDD
null HHHH DDDD DDDD
null ZZZZ DDDD DDDD
null null HHHH DDDD
null null ZZZZ DDDD
null null null HHHH
null null null ZZZZ
null null null null
null null null null
null null null null
...etc

What is a better way to approach this?

Answer 1

Try this

    String[] AA = {"DDDD", "HHHH", "ZZZZ"};
    String[] BB = {"DDDD", "HHHH", "ZZZZ"};
    String[] CC = {"DDDD", "HHHH", "ZZZZ"};
    String[] DD = {"DDDD", "HHHH", "ZZZZ"};


    String[][] result = new String[4][AA.length * BB.length * CC.length * DD.length];

    int row = 0;
    for (int i = 0; i < AA.length; i++) {

        for (int j = 0; j < BB.length; j++) {

            for (int k = 0; k < CC.length; k++) {

                for (int L = 0; L < DD.length; L++) {

                    result[3][row] = DD[L];
                    result[2][row] = CC[k];
                    result[1][row] = BB[j];
                    result[0][row] = AA[i];
                    System.out.println(result[0][row] + " " +result[1][row] + " " +result[2][row] + " " +result[3][row]);
                    row++;
                }
            }
        }
    }

and output

DDDD DDDD DDDD DDDD
DDDD DDDD DDDD HHHH
DDDD DDDD DDDD ZZZZ
DDDD DDDD HHHH DDDD
DDDD DDDD HHHH HHHH
DDDD DDDD HHHH ZZZZ
DDDD DDDD ZZZZ DDDD
...