获取 java.util.List 的泛型类型 [英] Get generic type of java.util.List

问题描述

我有；

List<String> stringList = new ArrayList<String>();
List<Integer> integerList = new ArrayList<Integer>();

有没有(简单的)方法来检索列表的泛型类型?

Is there a (easy) way to retrieve the generic type of the list?

推荐答案

如果这些实际上是某个类的字段，那么你可以通过一些反思来获得它们:

If those are actually fields of a certain class, then you can get them with a little help of reflection:

package test;

import java.lang.reflect.Field;
import java.lang.reflect.ParameterizedType;
import java.util.ArrayList;
import java.util.List;

public class Test {

    List<String> stringList = new ArrayList<String>();
    List<Integer> integerList = new ArrayList<Integer>();

    public static void main(String... args) throws Exception {
        Field stringListField = Test.class.getDeclaredField("stringList");
        ParameterizedType stringListType = (ParameterizedType) stringListField.getGenericType();
        Class<?> stringListClass = (Class<?>) stringListType.getActualTypeArguments()[0];
        System.out.println(stringListClass); // class java.lang.String.

        Field integerListField = Test.class.getDeclaredField("integerList");
        ParameterizedType integerListType = (ParameterizedType) integerListField.getGenericType();
        Class<?> integerListClass = (Class<?>) integerListType.getActualTypeArguments()[0];
        System.out.println(integerListClass); // class java.lang.Integer.
    }
}

您也可以对参数类型和方法的返回类型执行此操作.

You can also do that for parameter types and return type of methods.

但是如果它们在您需要了解它们的类/方法的同一范围内，那么了解它们就没有意义了，因为您已经自己声明了它们.

But if they're inside the same scope of the class/method where you need to know about them, then there's no point of knowing them, because you already have declared them yourself.

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