java泛型类继承问题?

Question

如题所示,想通过继承GeoResult类来扩展属性

   //GeoResult 类
public class GeoResult<T> implements Serializable {
    private static final long serialVersionUID = 1637452570977581370L;    
    private final T content;    private final Distance distance;   
     public GeoResult(T content, Distance distance) {
        Assert.notNull(content, "Content must not be null!");
        Assert.notNull(distance, "Distance must not be null!");        
        this.content = content;        
        this.distance = distance;
    }
}

//扩展GeoResult类
public class GeoExtendResult<T> extends GeoResult<T> implements Serializable{
 
    public GeoExtendResult(T content, Distance distance) {
        super(content, distance);
    }
}

//这是正确的
List<GeoResult<RedisGeoCommands.GeoLocation<String>>> geoResultList =  radiusGeo.getContent();
//报类型不匹配
List<GeoExtendResult<RedisGeoCommands.GeoLocation<String>>> geoResultList =  radiusGeo.getContent();

Answer 1

我倒是看懂了你想做什么，但你这问题描述的有点问题。泛型的特点是泛，给你举个例子吧
针对泛型接口：

GeoExtendResult extends GeoResult<?> //不限定泛型类型
GeoExtendResult extends GeoResult<RedisDemo.GeoList<String>  // 限定泛型类型为RedisDemo.GeoList<String> 

泛型类：

GeoExtResult<T> extends GeoResult<T> //子类也想用泛型必须添加泛型

第三次更新：

public class GenericT<T> implements Serializable {

    private static final long serialVersionUID = 1637452570977581370L;
    private final T content;
    private final String distance;

    public GenericT(T content, String distance) {
        this.content = content;
        this.distance = distance;
    }
}


public class GenericExtT<T> extends GenericT<T> {

    public GenericExtT(T content, String distance) {
        super(content, distance);
    }

    public List<GenericExtT<T>> getContent() {
        return Collections.unmodifiableList(Lists.newArrayList());
    }

    @Autowired GenericExtT genericExtT;
    public void main(String[] args){
        //这是正确的
        List<GenericExtT<? extends T>> geoResultList =  genericExtT.getContent();
    }

}