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Java泛型协方差与逆变

java generics

Java泛型协方差与逆变,java,generics,Java,Generics,代码中的内联问题 class A1{} class B1 extends A1{} class C1 {} public class X { public void meth(List<? super B1> l){ l.add(new A1());//why this is not a valid syntax,why we can only add new B1() ? } public void meth2(List<? ex

代码中的内联问题

class A1{}
class B1 extends A1{}
class C1 {}

public class X {

    public void meth(List<? super B1> l){
        l.add(new A1());//why this is not a valid syntax,why we can only add new B1() ?
    }

    public void meth2(List<? extends A1> l){
        //and here, why can't we add anything ?
    }
}

class A1{}
B1类扩展了A1{}
类别C1{}
公共X类{
公共无效方法（列表点
列表