java - Java泛型: Bound mismatch

我有一个具有此定义的通用类:

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

AntColony的运行方式如下:

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

Ant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> {

但是Eclipse在FlowShopAntColony参数类上显示了一个错误:

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像这样:

public class AntForFlowShop extends Ant<Integer, FlowShopEnvironment> {

为什么FlowShopAntColony不被接受为有效参数？

最佳答案

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

AcoProblemSolver的第三个参数具有限制extends AntColony<E, Ant<C, E>>。 AntColony的第二个参数必须是，确切地说是 Ant<C, E>，而您正在尝试传递Ant的子类。尝试:

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

您可能需要其他类似的? extends子句。