java - 复杂和不同数据结构的通用方法

Question

我想为复杂结构创建一个通用方法，但我不知道如何将该方法的签名与我的数据结构相匹配。

我有以下结构:

我正在使用的一个类:

public class Individual <T extends AnInterface> {

    final List<T> data;

    public Individual(final List<T> data){
        this.data = data;
    }
    public List<T> getData() {
        return data;
    }
}

我正在使用的较小结构:

public class Tuple3<T1,T2,T3> {

    public T1 _1;
    public T2 _2;
    public T3 _3;

    public Tuple3(T1 t1, T2 t2, T3 t3){
        _1 = t1;
        _2 = t2;
        _3 = t3;
    }

}

我想在其中使用泛型方法的泛型类:

class MyTemplatedClass <..., T2 extends AnInterface, ...> 
    implements ... {

    private Map<Integer,        List<Tuple3<Integer, Individual<T2>, Double>>> resultsByIteration;
    private Map<Individual<T2>, List<Tuple3<Integer, Individual<T2>, Double>>> resultsByIndividual;
    private int iteration = 0;

    @Override
    public <T2 extends AnInterface> void evaluatePopulationAndStoreResults(List<Individual<T2>> elements) {

        // changing iteration
        // calculating fitness
        for (Individual<T2> element : elements) {

            Tuple3<Integer, Individual<T2>, Double> triplet = new Tuple3<>(iteration, element, fitness);

            /// I want this operation to be templated for both strutures
            doSomeListOperationOnMapForAGivenKey(resultsByIteration,  new Integer(5), triplet);
            doSomeListOperationOnMapForAGivenKey(resultsByIndividual, elements, triplet);
        }
    }

    /// How should doSomeListOperationOnMapForAGivenKey() method's signature look like, if I want to call this on both data structures???
    // this signature does not match to the above calls :(
    public <KEY_TYPE, VALUE_TYPE> void doSomeListOperationOnMapForAGivenKey(Map<KEY_TYPE, List<VALUE_TYPE>> map, KEY_TYPE key, VALUE_TYPE value){
        // some list operation:
        // check if key is in map
          // if not, then create a list, add the value to the list and put the key and value into the map
          // if yes, then check if is there any similar tuple in the list under the key
            // it there is no similar tuple, then add the value to the list
            // if there is a similar tuple, then update with the value
    }

}

我收到此签名的编译错误:

 public <KEY_TYPE, VALUE_TYPE> void doSomeListOperationOnMapForAGivenKey(Map<KEY_TYPE, List<VALUE_TYPE>> map, KEY_TYPE key, VALUE_TYPE value)

如果我想对不同类型的两个结构执行相同的映射和列表操作，我无法弄清楚 doSomeListOperationOnMapForAGivenKey() 方法的签名应该是什么样子。我希望这个方法尽可能通用。有什么想法吗？

更新:感谢 Radiodef 的评论，修复了类定义中的错误，现在看起来像这样:

class MyTemplatedClass <..., T2 extends AnInterface, ...> 
    implements SomeOtherInterface<T2> {...}

调用者方法的签名如下:

@Override
public void evaluatePopulationAndStoreResults(List<Individual<T2>> elements) {...}

Answer 1

编译器错误试图告诉您的是，在类上声明的 T2 和在方法 evaluatePopulationAndStoreResults 上声明的 T2 引用了不同类型。

class MyTemplatedClass <..., T2 extends AnInterface, ...> 
    implements ... {

    @Override
    // Declares a new type variable T2, unrelated to the
    // T2 declared on the class and shadows it.
    //     vvvvvvvvvvvvvvvvvvvvvvvv
    public <T2 extends AnInterface> void evaluatePopulationAndStoreResults(...) {
        {

            Tuple3<Integer, Individual<T2>, Double> triplet =
                new Tuple3<>(iteration, element, fitness);

            doSomeListOperationOnMapForAGivenKey(resultsByIteration,
                                                 new Integer(5),
                                                 triplet);
        }
    }

实际发生的事情是这样的:

// One type variable declared on the class, used by
// both maps.
//                           vvvvvvvvvvvvvvvvvvvvvvv
class MyTemplatedClass <..., T2A extends AnInterface, ...> 
    implements ... {

    @Override
    // Another different type variable declared
    // on the method.
    //     vvvvvvvvvvvvvvvvvvvvvvvv
    public <T2B extends AnInterface> void evaluatePopulationAndStoreResults(...) {
        {

            Tuple3<Integer, Individual<T2B>, Double> triplet =
                new Tuple3<>(iteration, element, fitness);

            //                              Passing a Map using T2A
            //                                   vvvvvvvvvvvvvvvvvv
            doSomeListOperationOnMapForAGivenKey(resultsByIteration,
                                                 new Integer(5),
            //           Passing a Tuple3<..., T2B, ...>
            //                                   vvvvvvv
                                                 triplet);
        }
    }

但是在您的代码中，两个类型变量具有相同的名称。这与声明与实例成员同名的局部变量时发生的情况类似。

据我所知，您只需删除 evaluatePopulationAndStoreResults 上的类型变量声明即可。当您在类上声明类型变量时，整个类都可以访问它。

我认为如果删除隐藏类型变量声明，所示的代码片段应该可以编译。