Transformer-view java实体 转换视图 Lists.transform

Posted 2021-01-06 雪洗中关村

 

自： https://blog.csdn.net/mnmlist/article/details/53870520

 

meta_ws 连接： https://github.com/kse-music/demo/blob/064663ac7251285745dc915dad4a6837f723538f/src/test/java/com/hiekn/demo/test/util/GuavaTest.java

 

import com.google.common.base.Function;
import com.google.common.base.MoreObjects;
import com.google.common.base.Preconditions;
import com.google.common.cache.Cache;
import com.google.common.cache.CacheBuilder;
import com.google.common.cache.CacheLoader;
import com.google.common.cache.LoadingCache;
import com.google.common.collect.*;
import com.google.common.collect.Table.Cell;
import com.google.common.eventbus.AllowConcurrentEvents;
import com.google.common.eventbus.AsyncEventBus;
import com.google.common.eventbus.Subscribe;
//import com.google.common.graph.*;
//import com.hiekn.demo.test.TestBase;
import org.junit.Test;

import java.util.*;
import java.util.Map.Entry;
import java.util.concurrent.Callable;
import java.util.concurrent.Executors;

 
public class dd {
    public static void main(String[] args) {

        List<PersonDb> personDbs = Lists.newArrayList(
                new PersonDb("a1", 10),
                new PersonDb("a2", 20),
                new PersonDb("a3", 30)
        );
        //返回的列表是原有列表的一个转换视图，对原有集合的修改当然会反映到新集合中,transform是单向的，无法向结果列表中添加新元素
        List<PersonVo> personVos = Lists.transform(personDbs, new Function<PersonDb, PersonVo>() {
            @Override
            public PersonVo apply(PersonDb personDb) {
                return viewTransformer(personDb);
            }
        });
        for(PersonDb personDb : personDbs) {
            personDb.setMsg("dbs修改!");
        }
//        Collections.shuffle(personVos);//随机打乱原来的顺序，和洗牌一样
//        personVos = ImmutableList.copyOf(personVos);
        personVos = Lists.newArrayList(personVos);
        //我认为直接循环遍历、转换生成resultList在时间和空间复杂度上会更好。

        for(PersonVo personVo : personVos) {
            personVo.setMsg("Vos修改!");
        }

//        personVos.add(viewTransformer(new PersonDb("a5", 50)));
        personVos.forEach(s -> System.out.println("--2-> "+s));



    }



    public static PersonVo viewTransformer(PersonDb personDb) {
        Preconditions.checkNotNull(personDb, "[PersonDbToVo]personDb为null");
        PersonVo personVo = new PersonVo();
        personVo.setName(personDb.getName() + ",from Db");
        personVo.setAge(personDb.getAge());
        personVo.setMsg(personDb.getMsg());
        return personVo;
    }

    static class PersonDb {
        private String name;
        private int age;
        private String msg;
        public PersonDb(String name, int age){
            this.name = name;
            this.age = age;
        }

        public String getName() {
            return name;
        }

        public void setName(String name) {
            this.name = name;
        }

        public int getAge() {
            return age;
        }

        public void setAge(int age) {
            this.age = age;
        }

        public String getMsg() {
            return msg;
        }

        public void setMsg(String msg) {
            this.msg = msg;
        }
        @Override
        public String toString() {
            return MoreObjects.toStringHelper(this)
                    .add("name", name)
                    .add("age", age)
                    .add("msg", msg).toString();
        }
    }
    static class PersonVo {
        private String name;
        private int age;
        private String msg;

        public String getName() {
            return name;
        }

        public void setName(String name) {
            this.name = name;
        }

        public int getAge() {
            return age;
        }

        public void setAge(int age) {
            this.age = age;
        }

        public String getMsg() {
            return msg;
        }

        public void setMsg(String msg) {
            this.msg = msg;
        }

        @Override
        public String toString() {
            return MoreObjects.toStringHelper(this)
                    .add("name", name)
                    .add("age", age)
                    .add("msg", msg).toString();
        }
    }

}