Largest Surface

Largest Surface
Description
Write a program that finds the largest possible sequence of equal neighboring elements in a rectangular matrix and prints its size.

Input
On the first line you will receive the numbers N and M separated by a single space;
On the next N lines there will be M numbers separated with spaces - the elements of the matrix;
Output
Print the size of the largest area of equal neighboring elements
Constraints
3 <= N, M <= 1024
Sample tests
Input
5 6
1 3 2 2 2 4
3 3 3 2 4 4
4 3 1 2 3 3
4 3 1 3 3 1
4 3 3 3 1 1
Output
13

import java.util.Scanner;

public class LargestSurface {
    static int rows, cols;
    static int[][] matrix;
    static boolean[][] isVisited;
    static int maxSequence = 0;

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        String inputLine = scanner.nextLine();
        String[] inputStringArr = inputLine.split(" ");
        rows = Integer.parseInt(inputStringArr[0]);
        cols = Integer.parseInt(inputStringArr[1]);
        matrix = new int[rows][cols];
        isVisited = new boolean[rows][cols];

        for (int i = 0; i < rows; i++) {
            for (int j = 0; j < cols; j++) {
                matrix[i][j] = scanner.nextInt();
            }
        }
        System.out.println(getMaxSequence());
    }
    public static int calculateSurface(int[][] matrix, int row, int col, int currentNumber) {
        if (isValid(row, col)) {
            return 0;
        }
        if (isVisited(row, col, currentNumber)) {
            return 0;
        }
        int countNumbers = 1;

        isVisited[row][col] = true;
        countNumbers += calculateSurface(matrix, row - 1, col, currentNumber);
        countNumbers += calculateSurface(matrix, row + 1, col, currentNumber);
        countNumbers += calculateSurface(matrix, row, col - 1, currentNumber);
        countNumbers += calculateSurface(matrix, row, col + 1, currentNumber);
        return countNumbers;
    }

    public static boolean isValid(int row, int col) {
        return row < 0 || row >= rows || col < 0 || col >= cols;
    }
    public static boolean isVisited(int row, int col, int currentNumber) {
        return isVisited[row][col] || matrix[row][col] != currentNumber;
    }
    public static int getMaxSequence() {
        maxSequence = 0;
        for (int i = 0; i < rows; i++) {
            for (int j = 0; j < cols; j++) {
                if (!isVisited[i][j]) {
                    int surface = calculateSurface(matrix, i, j, matrix[i][j]);
                    maxSequence = Math.max(surface, maxSequence);
                }
            }
        }
        return maxSequence;
    }
}