Tree - Trying to find the best path from top to the bottom

import java.util.ArrayList;
import java.util.Random;

public class Tree {

    // Variable
    ArrayList < ArrayList <Integer> > matrix;

    // Constructor
    Tree(){
        matrix = new ArrayList < ArrayList <Integer> > ();
    }

    // Methods
    public void showStatus() {
        for(int i=0; i<matrix.size(); i++) {
            for(int j=0; j<matrix.get(i).size(); j++) {
                System.out.print(matrix.get(i).get(j) + " ");
            }
            System.out.println();
        }
    }

    public void fillWithElements() {
        // First, I have to consider about the size of the matrix
        // This will be also the size of each sub-matrix
        // I want this to be 5 <= size <= 8
        Random random = new Random();
        int size = random.nextInt(4) + 5;
        // First, I have to fill up my "big" list matrix with sub-matrices, that are lists/elements.
        for(int i=0; i<size; i++) {
            ArrayList <Integer> listElement = new ArrayList <Integer> ();
            matrix.add(listElement);
        }
        // Now, I am free to create
        for(int i=0; i<size; i++) {
            for(int j=0; j<size; j++) {
                // The variable "matrix.get(i)" is instance of list type
                matrix.get(i).add(random.nextInt(100));
            }
        }
    }

    public int findIndexOfFirstElement() {
        int min = matrix.get(0).get(0);
        int index = 0;
        for(int i=1; i<matrix.get(0).size(); i++) {
            if(matrix.get(0).get(i) < min) {
                min = matrix.get(0).get(i);
                index = i;
            }
        }
        return index;
    }

    public int findIndexOfNextElement(int indexI, int indexJ) {
        int sizeX = matrix.size();
        int sizeY = matrix.get(indexI).size();
        // Be careful to put "%" in the arguments of "get" instruction, in order to avoid overflow
        int first = matrix.get((indexI+1) % sizeX).get((indexJ-1) % sizeY);
        int second = matrix.get((indexI+1) % sizeX).get((indexJ) % sizeY);
        int third = matrix.get((indexI+1) % sizeX).get((indexJ+1) % sizeY);
        // Check the minimum of these 3 elements
        if(first <= second && first <= third) {
            return indexJ-1;
        }
        else if(second <= first && second <= third) {
            return indexJ;
        }
        else {
            return indexJ+1;
        }
    }

    public static ArrayList <Integer> findASmallPath(){
        ArrayList <Integer> indeces = new ArrayList <Integer> ();
        ArrayList <Integer> path = new ArrayList <Integer> ();
        // First, I select the first element
        int firstIndex = findIndexOfFirstElement();
        indeces.add(firstIndex);
        for(int i=0; i<matrix.size()-1; i++) {
            int indexIPlus1 = findIndexOfNextElement(i, indeces.get(i));
            indeces.add(indexIPlus1);
        }

        /*
        int secondIndex = findIndexOfNextElement(0, indeces.get(0));
        indeces.add(secondIndex);
        int thirdIndex = findIndexOfNextElement(1, indeces.get(1));
        indeces.add(thirdIndex);
        int fourthIndex = findIndexOfNextElement(2, indeces.get(2));
        indeces.add(fourthIndex);
        int fifthIndex = findIndexOfNextElement(3, indeces.get(3));
        indeces.add(fifthIndex);
        */

        for(int i=0; i<indeces.size(); i++) {
            path.add(matrix.get(i).get(indeces.get(i)));
        }
        return path;
    }


    // MAIN FUNCTION
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Tree tree = new Tree();
        tree.fillWithElements();
        System.out.println("**** Our Matrix is: ****");
        System.out.println();
        tree.showStatus();
        ArrayList <Integer> path = findASmallPath();
        for(int i=0; i<path.size(); i++) {
            if(i != path.size() - 1) {
                System.out.print(path.get(i) + " ----> ");
            }
            else {
                System.out.print(path.get(i));
            }
        }
    }

}