如何在构造函数中填充数组

Question

我有一辆客货车和一辆班车，它们有关系。我已经创建了一个货车数组，需要在列车构造函数中使用(据我所理解)，但我不理解h如何在构造函数中使用数组并填充数组以使代码运行

这是我的密码。谢谢你的解释！

public class Wagon {
    private int m;

    public int getM() {
        return m;
    }


    public Wagon(int m) {
        this.m = m;
    }


    private Wagon[] wag = new Wagon[3];

public class Train {

    private Wagon[] wag;

    public Train(Wagon[] wag){
        this.wag=wag;
    }


    public int findCargo() {

        int x = 0;

        for (Wagon w : wag) {

            x += w.getM();
        }

        return x;
    }


    public int findAverage() {

        return this.findCargo() / wag.length;
    }
}

    public static void main(String[] args) {
        Train train = new Train( new Wagon[]{8,9,7});
        System.out.println(train.findCargo());

Answer 1

你不懂数组的语法。

参考文献:：https://docs.oracle.com/javase/tutorial/java/nutsandbolts/arrays.html

// declares an array of integers
int[] anArray = { 100, 200, 300 };
// declares an array of String's
String[] strArray= { "100", "200", "300" };

如果您想创建Wagon数组，那么

Wagon[] wagons = new Wagon[]{new Wagon(8), new Wagon(9), new Wagon(7)};

将代码替换为

Wagon[] wagons = new Wagon[]{new Wagon(8), new Wagon(9), new Wagon(7)};
Train train = new Train(wegons);
System.out.println(train.findCargo());

Answer 2

可以使用变量参数语法。

public Train(Wagon... wag){
        this.wag=wag;
    }

然后你就可以这样称呼它

Train train = new Train(new Wagon(1), new Wagon(2), new Wagon(3));

Answer 3

这个new Wagon[]{8,9,7}不起作用，您尝试创建一个货车数组并将其填充到ints中。你需要用货车对象填充它

有效的是new Wagon[]{new Wagon(8), new Wagon(9), new Wagon(7)}

Wagon[] wagons = new Wagon[]{new Wagon(8), new Wagon(9), new Wagon(7)};
Train train = new Train(wagons);