Java - 泛型 - 在泛型指定对象中转换泛型对象不起作用

Question

我正在尝试解决这个看似简单的通用转换问题:

首先，声明这个简单的通用对象:

public interface GenericObject<T> {}

其次，声明这个工作接口(interface):

public interface Generic { // I don't want to do Generic<T>

    <T> void setGenericObject(GenericObject<T> obj);

}

然后，让我们实现这个接口(interface):

public class GenericImpl implements Generic {

    private GenericObject<String> genericObject; // This is needed

    @Override
    public <String> void setGenericObject(GenericObject<String> obj) {
        genericObject = obj; // eclipse give me this error :
                             // Type mismatch: cannot convert from 
                             // interfaces.GenericObject<String> to
                             // interfaces.GenericObject<java.lang.String>
    }

}

如何解决这个错误？

编辑:

实际上，解决这个问题的唯一方法就是这样做:

public class GenericImpl implements Generic {

    private GenericObject<String> genericObject; 

    @SuppressWarnings("unchecked") // I don't realy like this
    @Override
    public <T> void setGenericObject(GenericObject<T> obj) {
        genericObject = (GenericObject<String>) obj;
    }

}

Answer 1

真正的问题是

public <String> void setGenericObject(GenericObject<String> obj)

其中String与您想要的java.lang.String无关。这里的String只是一个类型参数，它的名字偶然是String。

请引用Is it possible to have an interface method defined with a generic return type and a concrete implementation define the return type? .