list转map(基于stream)

效果图

 代码

package springboot;

import org.junit.Test;
import java.util.Arrays;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;

/**
 * @author yourheart
 * @Description
 * @create 2022-06-12 21:06
 */
public class GoodsTests {


    @Test
    public void test001(){
        // 创建一个List集合
        List<FruitDTO> dtoList = Arrays.asList(
                new FruitDTO("apple", 5),
                new FruitDTO("banana", 6),
                new FruitDTO("orange", 6),
                new FruitDTO("grape", 5),
                new FruitDTO("kiwi", 4)
        );

        // 将List<FruitDTO>转换为Map，以DTO的name作为key，DTO对象本身作为value
        Map<String, FruitDTO> dtoMap = dtoList.stream()
                .collect(Collectors.toMap(
                        FruitDTO::getName, // key是FruitDTO对象的name属性
                        dto -> dto // value是FruitDTO对象本身
                ));
        // 输出转换后的Map
        dtoMap.forEach((name, dto) -> System.out.println(name + ": " + dto));

        Map<String, Integer> collect = dtoList.stream().collect(
                Collectors.toMap(FruitDTO::getName, FruitDTO::getLength)
        );
        collect.forEach((name, length) -> System.out.println(name + ": " + length));

    }

}

class FruitDTO {
    private String name;
    private int length;

    public FruitDTO(String name, int length) {
        this.name = name;
        this.length = length;
    }

    public String getName() {
        return name;
    }

    public int getLength() {
        return length;
    }

    @Override
    public String toString() {
        return "FruitDTO{" +
                "name='" + name + '\'' +
                ", length=" + length +
                '}';
    }
}

　　用到的pom依赖

<!--引入junit单元测试依赖-->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.13.2</version>
        </dependency>