Question

我在一个抽象类中定义了一个方法，如下所示，

public abstract class AbstractService {
    protected abstract <T> Message<T> executeService(Message<T> msg)
            throws ServiceException;

}

我想在具体的子类中实现此方法，如下所示，

public class RescheduleInfoAdaptor extends AbstractService {
    @Override
    protected Message<RescheduleInfo> executeService(Message<RescheduleInfo> msg)
            throws ServiceException {
        //implementation goes here
    }
}

但是编译器报告错误说

The method executeService(Message<RescheduleInfo>) of type RescheduleInfoAdaptor must override or implement a supertype method

有谁能建议如何在子类中实现所需类型的超类方法？

Answer 1

您有两种选择：

要么

将抽象方法类型参数上传到RescheduleInfo（或RescheduleInfo的某些特定超类，类似AbstractInfo）

例如：

protected abstract <T extends RescheduleInfo> Message<T> executeService(Message<T> msg)
        throws ServiceException;

但请注意，这将编译，但会生成＆＃34;类型安全＆＃34;警告。

或

使AbstractService泛型并删除抽象方法type-parameter。

例如：

public abstract class AbstractService<T> {
    protected abstract Message<T> executeService(Message<T> msg)
            throws ServiceException;

}

然后，在另一个课程中，您将拥有：

public class RescheduleInfoAdaptor extends AbstractService<RescheduleInfo> {
    @Override
    protected Message<RescheduleInfo> executeService(Message<RescheduleInfo> msg)
            throws ServiceException {
        //implementation goes here
    }
}

Answer 2

试试这样：

public abstract class AbstractService<T> {
       protected abstract Message<T> executeService(Message<T> msg)

和

public class RescheduleInfoAdaptor extends AbstractService<RescheduleInfo> {

Answer 3

您需要更改此

protected abstract <T> Message<T> executeService(Message<T> msg)

到此

protected abstract <T extends Something> Message<T extends Something> executeService(Message<T extends Something> msg)

Where Something是RescheduleInfo

的超类

覆盖java中的泛型方法

3 个答案: