这段时间我正在做一个需要某种抽象的项目,但我不知道如何解决一些与java泛型和类型推断相关的问题。
这是源代码的简化架构:
public abstract class BaseDataset
{
// Some data
// Some methods
}
public class DerivedDataset1 extends BaseDataset
{
// Some data
// Implementations of some BaseDataset methods
// Some additional methods
}
public class DerivedDataset2 extends BaseDataset
{
// Some data
// Implementations of some BaseDataset methods
// Some additional methods
}
public interface BaseMeasure<T extends BaseDataset>
{
public float evaluate(T dataset);
}
public class DerivedMeasure1 implements BaseMeasure<DerivedDataset1>
{
@Override
public float evaluate(DerivedDataset1 dataset)
{
// evaluate some measure using DerivedDataset1 methods
return the evaluated measure;
}
}
public class DerivedMeasure2 implements BaseMeasure<DerivedDataset2>
{
@Override
public float evaluate(DerivedDataset1 dataset)
{
// evaluate some measure using DerivedDataset2 methods
return the evaluated measure;
}
}
public class SocialNetworkBuilder
{
public <T extends BaseDataset> void build(T dataset, BaseMeasure<T> measure)
{
float weight = measure.evaluate(dataset);
// ...
}
}
我的问题是,如果在我的主类中,我写了这样的内容:
public class Application
{
public static void main(String [] args)
{
BaseDataset dataset = new DerivedDataset1();
BaseMeasure<? extends BaseDataset> measure = new DerivedMeasure1();
SocialNetworkBuilder socialNetworkBuilder = new SocialNetworkBuilder();
socialNetworkBuilder.build(dataset, measure);
}
}
Eclipse 给我错误:“SocialNetworkBuilder 类型中的方法 build(T, BaseMeasure) 不适用于参数 (BaseDataset, BaseMeasure)”
我认为问题在于“构建”方法必须确保数据集和度量属于同一类型 T。
如果我做这样的事情:
public class Application
{
public static void main(String [] args)
{
BaseDataset dataset = new DerivedDataset1();
BaseMeasure<? extends BaseDataset> measure = new DerivedMeasure1();
SocialNetworkBuilder socialNetworkBuilder = new SocialNetworkBuilder();
socialNetworkBuilder.build((DerivedDataset1) dataset, (DerivedMeasure1) measure);
}
}
它可以工作,但我无法以这种方式解决我的问题,因为我不知道编译时“数据集”和“测量”实例的派生类型; “dataset”和“measure”应该根据运行时给出的一些参数进行实例化。
我需要在运行时实例化我的“measure”和“dataset”变量,并且仍然能够调用它们的“build”方法。
您有解决这个问题的想法吗?
谢谢。
最佳答案
当您按如下方式更改时,您的应用程序将编译:
public class Application
{
public static void main(String [] args)
{
DerivedDataset1 dataset = new DerivedDataset1();
BaseMeasure<DerivedDataset1> measure = new DerivedMeasure1();
SocialNetworkBuilder socialNetworkBuilder = new SocialNetworkBuilder();
socialNetworkBuilder.build(dataset, measure);
}
}
关于java - 在 Java 中使用泛型和类型推断的问题,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/20163246/