Getting smallest of each arraylist

I'm doing a program to sort grades. It compares 3 arraylist of arrayslist and im trying to get the smallest nodes ones in 1, medium in 2 and larger in 3. Then save that to grade 1, 2 or 3.

The following code keeps repeating nodes. Anybody knows why? Any suggestions?

ArrayList<ArrayList<Double>> y = new ArrayList<ArrayList<Double>>(); // ->have 10 nodes in them of 10 elements each
ArrayList<ArrayList<Double>> y2 = new ArrayList<ArrayList<Double>>(); // ->have 10 nodes in them of 10 elements each
ArrayList<ArrayList<Double>> y3 = new ArrayList<ArrayList<Double>>(); // ->have 10 nodes in them of 10 elements each

for (int j = 0; j < y.size(); j++) {
    for (int k = 0; k < y.get(j).size(); k++) {
        if (y.get(j).get(k) < y2.get(j).get(k) && y.get(j).get(k) < y3.get(j).get(k)) {
            grades.get(j).remove(14);
            grades.get(j).add(14, 1.00);
            grades2.add(grades.get(j));
        }
        if (y2.get(j).get(k) < y3.get(j).get(k)) {
            grades.get(j).remove(14);
            grades.get(j).add(14, 2.00);
            grades2.add(grades.get(j));

        } else {
            grades.get(j).remove(14);
            grades.get(j).add(14, 3.00);
            grades3.add(grades.get(j));
        }
    }
}