Java泛型：绑定不匹配

Question

我有一个具有此定义的泛型类：

public class AcoProblemSolver<C, E extends Environment, A extends AntColony<E, Ant<C, E>>> {

AntColony就是这样的：

public abstract class AntColony<E extends Environment, A extends Ant<?, E>> {

Ant就像这样：

public abstract class Ant<C, E extends Environment> {

我希望以这种方式扩展AntColony ：

public class FlowShopProblemSolver extends
    AcoProblemSolver<Integer, FlowShopEnvironment, FlowShopAntColony> {

但Eclipse在FlowShopAntColony参数类上显示错误：

Bound mismatch: The type FlowShopAntColony is not a valid substitute for the bounded parameter <A extends AntColony<E,Ant<C,E>>> of the type AcoProblemSolver<C,E,A>

这让我感到困惑，因为FlowShopAntColony是这样定义的：

public class FlowShopAntColony extends
    AntColony<FlowShopEnvironment, AntForFlowShop> {

AntForFlowShop是这样的：

public class AntForFlowShop extends Ant<Integer, FlowShopEnvironment> {

为什么FlowShopAntColony不被接受为有效参数？

Answer 1

A extends AntColony<E, Ant<C, E>>

AcoProblemSolver的第三个参数有限制extends AntColony<E, Ant<C, E>> AcoProblemSolver extends AntColony<E, Ant<C, E>> 。 AntColony的第二个参数必须完全是 Ant<C, E>并且您正在尝试传递Ant的子类。 尝试：

A extends AntColony<E, ? extends Ant<C, E>>

你可能想要其他类似的? extends 在其他地方? extends条款。