覆盖Java中的通用方法

Question

我在一个抽象类中定义了一种方法，如下所示：

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

}

我想在一个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

谁能建议我如何在子类中以所需类型实现超类方法？

Answer 1

您有两种选择：

要么

• 向上结合的抽象方法类型参数RescheduleInfo （或一些具体的超RescheduleInfo ，像AbstractInfo ）

例如：

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

但是，请注意，这将编译，但会生成“类型安全”警告。

要么

• 使AbstractService通用，并删除抽象方法的type-parameter。

例如：

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

}

然后，在另一堂课中，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

像这样尝试：

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

和

public class RescheduleInfoAdaptor extends AbstractService<RescheduleInfo> {

Answer 3

你需要改变这个

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

对此

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

某物是RescheduleInfo的超类