[英]Java inheritance and generics
I'm trying to extend an abstract class with generics and I'm running into a problem: 我正在尝试使用泛型扩展抽象类,但遇到了一个问题:
abstract public class SomeClassA<S extends Stuff> {
protected ArrayList<S> array;
public SomeClassA(S s) {
// ...
}
public void someMethod() {
// Some method using the ArrayList
}
abstract public void anotherMethod() {
// ...
}
}
Now I want to extend this class with another abstract class so I could override "someMethod". 现在,我想用另一个抽象类扩展该类,以便覆盖“ someMethod”。 I tried:
我试过了:
abstract public class SomeClassB<Z extends Stuff> extends SomeClassA {
public SomeClassB(Z z) {
super(z);
}
@Override public void someMethod() {
// Some method using the ArrayList
}
}
NetBeans doesn't see any problem with the constructor, but I cannot use the ArrayList from SomeClassA within the method someMethod. NetBeans认为构造函数没有任何问题,但是我无法在someMethod方法中使用SomeClassA的ArrayList。 So I tried:
所以我尝试了:
abstract public class SomeClassB<Z extends Stuff> extends SomeClassA<S extends Stuff> {
public SomeClassB(Z z) {
super(z);
}
@Override public void someMethod() {
// Some method using the ArrayList
}
}
And now it's just very odd. 现在,这很奇怪。 Everything seems to work (and I can now use the arraylist, but NetBeans says there's a "> expected" in the declaration of SomeClassB and it just won't compile. If possible, I would like:
一切似乎都正常(并且我现在可以使用arraylist了,但是NetBeans表示SomeClassB的声明中有一个“>”,它不会被编译。如果可能的话,我想:
To know how to solve this particular problem. 要知道如何解决这个特定问题。
To have a good reference to understand generics. 很好地了解泛型。
To know if it's any easier in C#. 要知道在C#中是否更简单。
You will need to pass the generic type to the superclass also, like this: 您还需要将泛型类型传递给超类,如下所示:
abstract public class SomeClassB<Z extends Stuff> extends SomeClassA<Z>
Your superclass and subclass will then both use the same generic type. 然后,您的超类和子类都将使用相同的泛型类型。 Generic Types are not inherited by subclasses or passed down to superclasses.
泛型类型不被子类继承或传递给超类。
为了更好地理解泛型,请参阅有效的Java,第二版 。
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