一个类可以没有构造函数吗？ [英] Can a class have no constructor?

问题描述

这是一段代码作为一个例子，其余的只是方法（看迷宫类的底部）。因此，当实例化时，使用

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();

和

System.out.println (labyrinth);

这将打印出网格数组。
这是合法的吗？我认为所有类都需要构造函数如何打印2-d网格数组？

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?

迷宫类：

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

}

推荐答案

显式定义构造函数不是必需的;但是，所有类都必须有一个构造函数，如果你不提供任何类，将生成一个默认的空构造函数：

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() {
}

参见默认构造函数。

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