泛型自限定

class SelfBounded<T extends SelfBounded<T>>{
    T element;
    SelfBounded<T> set(T arg){
        element = arg;
        return this;
    }
    T get() {
        return element;
    }
}
class D{}
class A extends SelfBounded<A>{}
// class E extends SelfBounded<D>{} 会报错

格式: class SelfBounded<T extends SelfBounded<T>>

自限定会强制要求正在定义的类当做参数传递给基类.看格式就能看出来.

2.参数协变

 

interface SelfBoundSetter<T extends SelfBoundSetter<T>>{
    void set(T arg);
}

interface Setter extends SelfBoundSetter<Setter>{
    
}

public class SelfBoundingAndCovarianArguments {
    void testA(Setter s1 , Setter s2 ,SelfBoundSetter sbs) {
        s1.set(s1);
        s1.set(s2);
        // s1.set(sbs); 编译错误
    }
}

 

通过泛型自限定可以可以限制参数使用定义的类.