找能去的所有0区域

给一个二维matrix，-1代表墙，0代表路。问给定一个起点坐标为0，是否能到达所有的0。

public class AllReachableZero {
    

    public boolean findAllReachableZero(int[][] matrix, int x, int y)
    {
        boolean[][] visited = new boolean[matrix.length][matrix[0].length];
        dfs(matrix, x, y, visited);
        for(int i = 0; i< matrix.length; i++)
        {
            for(int j = 0; j< matrix[0].length; j++)
            {
                if(!visited[i][j] && matrix[i][j] == 0)
                {
                    return false;
                }
            }
        }
        return true;
    }

    public void dfs(int[][] matrix, int i, int j, boolean[][] visited)
    {
        if(!isBound(matrix, i, j) || visited[i][j] || matrix[i][j] == -1 || matrix[i][j] == 1)
        {
            return;
        }

        visited[i][j] = true;
        matrix[i][j] = 1;
        dfs(matrix, i-1, j, visited);
        dfs(matrix, i+1, j, visited);
        dfs(matrix, i, j-1, visited);
        dfs(matrix, i, j+1, visited);
    }

    public boolean isBound(int[][] matrix, int i, int j)
    {
        return i>=0 && i<matrix.length && j>=0 && j<matrix[0].length;
    }
}