如何使用泛型并从父类继承而不引起名称冲突? [英] How to use generics and inherit from parent class without causing name clash?
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 $ c>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
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.
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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