0807strem流试炼3--持续更新

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package util;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
import lombok.extern.log4j.Log4j2;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringRunner;

import java.util.*;
import java.util.function.Function;
import java.util.stream.Collectors;

//strem流试炼
@SpringBootTest
public class StreamTest {

    private  Logger logger  = LoggerFactory.getLogger(this.getClass());

    //一个接口中存放多个对象--一般用于一个entity实体类以外所有关的vo（值对象）、dto（数据传输对象）等对象都可以存放在一起（类少些了，也方便查询和删改）
    public interface  CollectionData{

        @Data
        @NoArgsConstructor
        @AllArgsConstructor
        public class A{
            private Long id;
            private String name;
            private Long age;
            private String sex;

            public A(String name, Long age, String sex) {
                this.name = name;
                this.age = age;
                this.sex = sex;
            }
        }


        @Data
        @NoArgsConstructor
        @AllArgsConstructor
        public class ADTO{
            private Long age;
            private String sex;
        }

    }


    //stream().sorted() 排序

    @Test
    public void streamSorted(){
        ArrayList<CollectionData.A> aLists = new ArrayList<>();
        CollectionData.A a1 = new CollectionData.A("小明", 1l, "男");
        CollectionData.A a2 = new CollectionData.A("小明3", 2l, "男2");
        CollectionData.A a3 = new CollectionData.A("小明3", 3l, "男3");
        CollectionData.A a4 = new CollectionData.A("小明3", 3l, "男3");
        aLists.add(a1);
        aLists.add(a2);
        aLists.add(a3);
        aLists.add(a4);



        //根据某个字段进行排序-升序，age
        List<CollectionData.A> collect = aLists.stream().sorted(Comparator.comparing(CollectionData.A::getAge)).collect(Collectors.toList());
        logger.info("{}",collect);
        //[StreamTest.CollectionData.A(id=null, name=小明, age=1, sex=男),
        // StreamTest.CollectionData.A(id=null, name=小明3, age=2, sex=男2),
        // StreamTest.CollectionData.A(id=null, name=小明3, age=3, sex=男3),
        // StreamTest.CollectionData.A(id=null, name=小明3, age=3, sex=男3)]

        //如果是倒叙-最常用的,.reversed() 反转
        List<CollectionData.A> collectReversed = aLists.stream().sorted(Comparator.comparing(CollectionData.A::getAge).reversed()).collect(Collectors.toList());
        logger.info("{}",collectReversed);

        //[StreamTest.CollectionData.A(id=null, name=小明3, age=3, sex=男3),
        // StreamTest.CollectionData.A(id=null, name=小明3, age=3, sex=男3),
        // StreamTest.CollectionData.A(id=null, name=小明3, age=2, sex=男2),
        // StreamTest.CollectionData.A(id=null, name=小明, age=1, sex=男)]


        //如果是单个字段，可以直接自然排序-升序
        List<Long> collectNaturalOrder = aLists.stream().map(m -> m.getAge()).sorted(Comparator.naturalOrder()).collect(Collectors.toList());
        logger.info("{}",collectNaturalOrder);
        //[1, 2, 3, 3]

        //如果是单个字段，可以直接反转-降序
        List<Long> collectReverseOrder = aLists.stream().map(m -> m.getAge()).sorted(Comparator.reverseOrder()).collect(Collectors.toList());
        logger.info("{}",collectReverseOrder);
        //[3, 3, 2, 1]

    }

}