java - Can a class have no constructor?

Question

This is a piece of code as an example, after this rest are just methods (look at bottom for maze class). So when this is instantiated, using

Maze labyrinth = new Maze();

and

System.out.println (labyrinth);

This will print out the grid array. Is this legit? I thought all classes needed constructors how does it print out the 2-d grid array?

Maze Class:

public class Maze
{
    private final int TRIED = 3;
    private final int PATH = 7;
    private int[][] grid = { {1,1,1,0,1,1,0,0,0,1,1,1,1},
                             {1,0,1,1,1,0,1,1,1,1,0,0,1},
                             {0,0,0,0,1,0,1,0,1,0,1,0,0},
                             {1,1,1,0,1,1,1,0,1,0,1,1,1},
                             {1,0,1,0,0,0,0,1,1,1,0,0,1},
                             {1,0,1,1,1,1,1,1,0,1,1,1,1},
                             {1,0,0,0,0,0,0,0,0,0,0,0,0},
                             {1,1,1,1,1,1,1,1,1,1,1,1,1} };

    public String toString ()
    {
        String result = "
";
        for (int row = 0; row < grid.length; row++)
        {
            for (int column=0; column < grid[row].length; column++)
            result += grid[row][column] + "";
            result += "
";
        }
        return result;
    }

}

Answer 1

It is not required to explicitly define a constructor; however, all classes must have a constructor, and a default empty constructor will be generated if you don't provide any:

public Maze() {
}

See Default Constructor.