java - 泛型中的父类(super class)型转换(获取泛型类型的泛型父类(super class)型)

Question

这是我尝试使用 Java Generics 进行的简化示例。

void <T> recursiveMethod(T input) {
    //do something with input treating it as type T
    if (/*need to check if T has a supertype*/) {
        recursiveMethod((/*need to get supertype of T*/) input);

        // NOTE that I am trying to call recursiveMethod() with
        // the input object cast as immediate supertype of T.
        // I am not trying to call it with the class of its supertype.
        // Some of you seem to not understand this distinction.
    }
}

如果我们有一个很长的类型链A extends B extends C(extends Object)，调用recursiveMethod(new A())应该执行如下:

recursiveMethod(A input)
 -> A has supertype B
recursiveMethod(B input)
 -> B has supertype C
recursiveMethod(C input)
 -> C has supertype Object
recursiveMethod(Object input)
 -> Object has no supertype -> STOP

我能够不泛型，如下所示:

void recursiveMethod(Object input) {
    recursiveMethod(input.getClass(), input);
    }
}

private void recursiveMethod(Class cls, Object input) {
    //do something with input treating it as class 'cls'
    if (cls != null) {
        recursiveMethod(cls.getSuperclass(), input);
    }
}

我可以使用泛型做同样的事情吗？我试过声明为 <S, T extends S> , 然后转换为 (S)input但是S始终等于 T并导致堆栈溢出。

Answer 1

这里有一个可以解决您的问题的迭代方法:

public static <T> void iterateOverSupertypes(T input) {
    Class<?> clazz = input.getClass();
    while (clazz.getSuperclass() != null) {
        clazz = clazz.getSuperclass();
    }
}