如何使用泛型并从父类继承而不导致名称冲突? [英] How to use generics and inherit from parent class without causing name clash?

问题描述

我在 Java 中有一个名为 Flight 的父类.我有子类:JetFlight、NormalFlight 等，它们继承自 Flight.

I have a parent class in Java called Flight. I have children classes: JetFlight, NormalFlight, etc. which inherit from Flight.

我希望所有子类都从 Comparable 接口实现 compareTo.我希望它们继承自 Flight 因为我想使用多态性(例如，启动一个 Flight 数组并用 JetFlight 的对象填充它，NormalFlight 等).

I want all the children classes to implement compareTo from the Comparable interface. I want them to inherit from Flight because I want to use polymorphism (for example, initiate a Flight array and fill it with objects of JetFlight, NormalFlight, etc.).

这是我的父类代码:

public abstract class Flight  {
    public abstract int compareTo(Object o);
}

这是其中一个子类的代码:

and this is the code for one of the children classes:

public class JetFlight extends Flight implements Comparable<JetFlight> {
    private int flightTime;
    public JetFlight(int flightTime) {
        this.flightTime = flightTime;
    }
    public int compareTo(JetFlight j) {
        return this.flightTime - j.flightTime;
    }
}

由于 2 个错误，此代码无法编译:

This code won't compile because of 2 errors:

1) 'java.lang.Comparable' 中的compareTo(T) 与'Flight' 中的'compareTo(Object)' 冲突；两个对象具有相同的擦除，但都不覆盖另一个.

2) 类 'JetFlight' 必须声明为抽象或在 'Flight' 中实现抽象方法 'compareTo(Object)'

如果我想继承一个类，同时在子类上使用泛型，我该如何处理?

How do I go about the situation when I want to inherit from a class and at the same time use generics on the child class?

推荐答案

选项 1:由于您的比较基于飞行时间，据我所知，变量飞行时间可以在父类中向上推，因为所有航班都将具有此功能.然后在父类中实现你的 compareTo() 方法.

Option 1: Since your comparison is based upon flight time, and as far as I know, the variable flightTime can be pushed up in the parent class as all flights will have this feature. Then implement your compareTo() method in parent class itself.

选项 2:如果您想保持当前代码不变:

Option 2: in case you want to keep your current code the way it is:

    public abstract class Flight implements Comparable<Flight> {
    public abstract int compareTo(Flight o);
}

<小时>

public class JetFlight extends Flight {
private int flightTime;
public JetFlight(int flightTime) {
    this.flightTime = flightTime;
}
public int compareTo(Flight f) {
    if(!(f instanceof JetFlight)){
        throw new IllegalArgumentException();
    }
    return this.flightTime - ((JetFlight)f).flightTime;
}

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