获取java.util.List的泛型类型 [英] Get generic type of java.util.List
本文介绍了获取java.util.List的泛型类型的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
我有;
列表< String> stringList = new ArrayList< String>();
列表<整数> integerList = new ArrayList< Integer>();
有没有一种(简单)的方法来检索列表的通用类型?
解决方案
如果这些实际上是某个类的字段,那么可以通过一些反射来获得它们:
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>();
列表<整数> 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); //类java.lang.String。
字段integerListField = Test.class.getDeclaredField(integerList);
ParameterizedType integerListType =(ParameterizedType)integerListField.getGenericType();
Class<?> integerListClass =(Class<> integerListType.getActualTypeArguments()[0];
System.out.println(integerListClass); //类java.lang.Integer。
$ / code $ / pre
你也可以为参数类型和返回类型如果他们在你需要了解他们的类/方法的相同范围内,那么就没有必要了解它们,因为你已经宣布他们自己。
I have;
List<String> stringList = new ArrayList<String>();
List<Integer> integerList = new ArrayList<Integer>();
Is there a (easy) way to retrieve the generic type of the list?
解决方案 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.
}
}
You can also do that for parameter types and return type of methods.
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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