如何使用另一个类的方法

Question

我想添加这个方法（它位于我的 Houses 类中）

public void step() {
    for (int i = 0; i < size; i++) {
        for (int j = 0; j < size; j++) {
            // Who are my neighbors
            House[][] ns = neighbors(houses[i][j]);

            // How many are red, blue
            int countRed = 0;
            int countBlue = 0;
            for (int n = 0; n < 8; n++) {
                if (ns[j][j].who == HouseType.Red) {
                    countRed = countRed + 1;
                }
                if (ns[j][j].who == HouseType.Blue) {
                    countBlue = countBlue + 1;
                }
            }
            // Decide to stay or move
            if (houses[i][j].decide(countRed, countBlue)) {
                houses[i][j].move(ns);
            }
        }
    }
}

到这个班级（ghetto 班级，这是我的主要班级）

    startButton = new JButton("start");
    add(startButton);
    startButton.addActionListener(new ActionListener() {
        @Override
        public void actionPerformed(ActionEvent e) {
            // Create a timer
            time = new javax.swing.Timer((int) (1000 * deltaT), this);
            time.start();
            // Add a listener for the timer - which is the step method
            if (e.getSource() == time) 
            {
                Houses h = new Houses();
                h.step();
                //Houses.step();
            }

        }
    });

所以我想要的是在我的主类 ghetto 中使用 step 方法（位于我的 Houses 类中），在这里它给出错误：

           Houses h = new Houses();
           h.step();

它说构造函数 Houses() 未定义。

Answer 1

您需要为Houses类添加一个默认构造函数。

在房屋类中：

public Houses() {

}

您可能有一个，看看您的类，您可能使用 netBeans 或 Eclipse 自动生成它，因此它将所有类属性作为参数。

看看OOP原理：

A类房子

public class House {
    int numberOfPeopleInHouse = 2;
    int numberOfDog = 0;

    public House() {
        //default constructor does nothing but creating a house.
    }
    public House(int dogCount) {
        this.numberOfDog = dogCount;
        /* This particular constructor take a int as parameter, and instead of creating
         * a simple house, we create an house with a modified dog count.
         */
    }
    public void addPeople(int numberOfPeople) {
        this.numberOfPeopleInHouse = this.numberOfPeopleInHouse + numberOfPeople;
    }
}

在你的主要

static void main(string[] args) {
    House firstHouse = new House(1);
    //firstHouse contains 2 people and 1 dog

    House secondHouse = new House();
    //secondHouse contains 2 people and 0 dog

    secondHouse.addPeople(2);
    //secondHouse contains 4 people and 0 dog
}

Answer 2

如您在其他问题中提供的代码所示， Houses的构造函数是：

public Houses(int size, int blue, int red) { ... }

它需要这三个参数，因此您必须提供它们，它们似乎是方形房屋网格边的大小以及蓝色和红色房屋的初始数量。 所以也许：

Houses h = new Houses(5, 3, 3);
h.step();