Question

大家好我只是java的初学者，我想覆盖这样的超类方法：

public class ShippedOrder extends Order{
    private final int ship = 15;

    public ShippedOrder(String cusName, int cusNo, int qty, double unitPrice, int ship){
        super(cusName, cusNo, qty, unitPrice);
    }

    public void setShip(int ship){
        super.computePrice() + ship;
    }
}

但是消息显示"+ is not a statement"。

Answer 1

您的代码没有任何意义：

public void setShip(int ship){
        super.computePrice() + ship;
}

super.computePrice()是一个返回内容或返回void的函数。您正在为其添加int，但您没有对其进行任何操作。假设此函数返回100.0。然后它等同于行100.0 + 15;这不是Java中的语句。

我假设您希望ShippedOrder将Order的价格增加ship。如果是这样，我建议删除setShip函数，并在调用Order的构造函数时传递unitPrice + ship：

public ShippedOrder(String cusName, int cusNo, int qty, double unitPrice, int ship){
    super(cusName, cusNo, qty, unitPrice+ship);
}

如果您不想这样做，请考虑在shipPrice中保留值ShippedOrder并在构造函数中设置它。

public ShippedOrder(String cusName, int cusNo, int qty, double unitPrice, int ship){
    super(cusName, cusNo, qty, unitPrice);
    this.shipPrice = ship;
}

Answer 2

这是我的猜测：

在Order类（父类）中，它具有computePrice()方法。我认为它是一个计算＆amp;退货价格：

// Assume in your "Order" class, you have:
public double computePrice() {
    // whatever calculation here ....
    double price = this.qty * this.unitPrice;

    return price;
}

然后现在你有ShippedOrder类，它扩展了Order类。您添加了ship作为新成员变量。如果您想将ship值添加到computePrice（）返回的价格，您可以尝试这样做：

public class ShippedOrder extends Order {
    // this is declared final, so it's value can only be set once in constructor
    // I would just declare it as double just to follow unitPrice type.
    private final double ship;

    public ShippedOrder (String cusName, int cusNo, int qty, double unitPrice, double ship) {
        super(cusName, cusNo, qty, unitPrice);

        // assign value pass in to member variable
        this.ship = ship;
    }

    @Override
    public double computePrice() {
        return super.computePrice() + this.ship;
    }
}

然后这样打电话：

ShippedOrder shippedOrder = new ShippedOrder("MyName", 100, 2, 200.5, 15);
double price = shippedOrder.computePrice();

希望这有帮助，祝你好运！

如何覆盖超类方法

2 个答案: