stream不能对有泛型的类做倒叙排序？

Question

public class TempTest {
    public static void main(String[] args) {
        //创建数据,对根据姓名 name 去重
        List<DemoDTO> allList = new ArrayList<>();

        allList.add(new DemoDTO("d1", "10"));
        allList.add(new DemoDTO("d2", "20"));
        allList.add(new DemoDTO("d3", "30"));

        allList.stream().sorted(Comparator.comparing(DemoDTO::getAge).reversed());
    }
}


@Data
class DemoDTO<T> {
    String name;
    String age;
    public DemoDTO(String name, String age) {
        this.name = name;
        this.age = age;
    }
}

Answer 1

 

import lombok.Data;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Comparator;
import java.util.List;
import java.util.stream.Collectors;

public class TempTest {
    public static void main(String[] args) {
        //创建数据,对根据姓名 name 去重
        List<DemoDTO<Object>> allList = new ArrayList<>();
        allList.add(new DemoDTO<>("d1", "10", null));
        allList.add(new DemoDTO<>("d2", "20", null));
        allList.add(new DemoDTO<>("d3", "30", null));
        System.out.println("前:[" + Arrays.toString(allList.toArray()) + "]");
        allList = allList.stream().sorted(Comparator.comparing(DemoDTO<Object>::getAge).reversed()).collect(Collectors.toList());
        System.out.println("后:[" + Arrays.toString(allList.toArray()) + "]");
    }
}

@Data
class DemoDTO<T> {
    String name;
    String age;
    T generic;

    public DemoDTO(String name, String age, T generic) {
        this.name = name;
        this.age = age;
        this.generic = generic;
    }
}

解决方式：添加泛型, 望采纳

 

运行结果：