如何使用泛型并从父类继承而不引起名称冲突？

问题描述

我有一个名为 Flight 的Java父类。我有子类： JetFlight ， NormalFlight 等等，它们继承自 Flight 。

我希望所有子类都可以从 Comparable 中实现 compareTo $ c>界面。我希望它们从 Flight 继承，因为我想使用多态性（例如，启动一个 Flight 数组并填充它对象 JetFlight ， NormalFlight 等）。

这是我父类的代码：

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

以下是其中一个子类的代码：

  public class JetFlight扩展了Flight implements Comparable< JetFlight> {
 private int flightTime; 
 public JetFlight（int flightTime）{
 this.flightTime = flightTime; 
} 
 public int compareTo（JetFlight j）{
 return this.flightTime  -  j.flightTime; 
 
 
 
 
 
 
 $ b 
由于2个错误，此代码无法编译：在'Flight'中与'compareTo（Object）'冲突;在'java.lang.Comparable'中的compareTo（T）与'FlightTo'中的'compareTo（Object）'冲突。这两个对象都有相同的擦除，但都不会覆盖另一个对象。 
 
 
 
 2） Class'JetFlight'必须是在'Flight'中声明抽象或实现抽象方法'compareTo（Object）' 
 
 
 
如果我想继承从一个类，同时在子类中使用泛型？
解决方案
选项1：由于您的比较基于飞行时间，据我所知，变量
  flightTime  
可以在父类中上推，因为所有航班都具有此功能。然后在父类本身中实现您的compareTo（）方法。
 
 
 
选项2：如果您想保持当前代码的使用方式：
  public abstract class Flight implements Comparable< Flight> {
 public abstract int compareTo（Flight o）; 
 
  
 
 
 
 
 
 
  public class JetFlight扩展了Flight {
 private int flightTime; 
 public JetFlight（int flightTime）{
 this.flightTime = flightTime; 
} 
 public int compareTo（Flight f）{
 if（！（f instanceof JetFlight））{
 throw new IllegalArgumentException（）; 
} 
返回this.flightTime  - （（JetFlight）f）.flightTime; 
} 
  
 
I have a parent class in Java called Flight. I have children classes: JetFlight, NormalFlight, etc. which inherit from Flight. 
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.). 
This is my code for the parent class:
public abstract class Flight  {
    public abstract int compareTo(Object o);
}
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;
    }
}
This code won't compile because of 2 errors:
1) compareTo(T) in 'java.lang.Comparable' clashes with 'compareTo(Object)' in 'Flight'; both objects have the same erasure, yet neither overrides the other.
2) Class 'JetFlight' must either be declared abstract or implement abstract method 'compareTo(Object)' in 'Flight'
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?
 解决方案 
Option 1: Since your comparison is based upon flight time, and as far as I know, the variable flightTimecan be pushed up in the parent class as all flights will have this feature. Then implement your compareTo() method in parent class itself.
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);
}
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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