Question

I tried doing:

for (int i=0; i<matrix.length; i++) {
  for (int j=0; j<matrix[].length; j++) {

but that doesn’t work 🙁

Answer 1

Just index into the matrix using your current row.

for (int i=0; i<matrix.length; i++) {
  for (int j=0; j<matrix[i].length; j++) {
    // code
  }
}

This even factors in the possibility of a jagged array (i.e., a matrix with an inconsistent number of rows in the column).