JAVA8 STREAM COLLECT GROUPBY分组实例解析
这篇文章主要介绍了JAVA8STREAMCOLLECTGROUPBY分组实例解析,文中通过示例代码介绍的非常详细，对大家的学习或者工作具有一定的参考学习价值,需要的朋友可以参考下
实体类People，有个返回list的buildPeopleList方法，方便测试。
importlombok.AllArgsConstructor;
importlombok.Builder;
importlombok.Data;
importlombok.NoArgsConstructor;
importjava.util.ArrayList;
importjava.util.Arrays;
importjava.util.List;
/**
*@author:rhyme
*@date:2019-09-2617:31
*@topic:"主题"
*@description:"描述"
*/
@Data
@NoArgsConstructor
@AllArgsConstructor
@Builder
publicclassPeople{
privateStringname;
privateStringcharacter;
privateStringsex;
privateintage;
publicstaticPeoplebuildDefault(){
returnPeople.builder().name("LuoTianyan").character("optimistic").sex("female").age(24).build();
}
publicstaticListbuildPeopleList(){
Peoplep1=People.builder().name("LuoTianyan").character("optimistic").sex("female").age(24).build();
Peoplep2=People.builder().name("Zhang").character("optimistic").sex("female").age(23).build();
Peoplep3=People.builder().name("Hu").character("shy").sex("female").age(25).build();
Peoplep4=People.builder().name("Y").character("Righteous").sex("male").age(24).build();
returnnewArrayList<>(Arrays.asList(p1,p2,p3,p4));
}
}
测试类GroupByTest，分别根据性别分组，统计各个性别人数，以及各个性别映射姓名。
importorg.junit.After;
importorg.junit.Before;
importorg.junit.Test;
importorg.springframework.util.CollectionUtils;
importjava.util.List;
importjava.util.Map;
importjava.util.function.BiConsumer;
importjava.util.stream.Collectors;
/**
*@author:rhyme
*@date:2019-10-1415:59
*@topic:"主题"
*@description:"描述"
*/
publicclassGroupByTest{
privateListpeople;
privateBiConsumersoutKV;
privateMapresult;
@Before
publicvoidinit(){
people=People.buildPeopleList();
soutKV=(k,v)->System.out.println(k+":"+v);
}
@After
publicvoidsoutResult(){
if(!CollectionUtils.isEmpty(result)){
result.forEach(soutKV);
}
}
/**
*根据性别分组
*/
@Test
publicvoidgroupBySex(){
result=people.stream().collect(
Collectors.groupingBy(People::getSex)
);
}
/**
*分别统计不同性别各自的人数
*/
@Test
publicvoidgroupBySexCount(){
result=people.stream().collect(
Collectors.groupingBy(People::getSex,Collectors.counting()
));
}
/**
*分别统计不同性别各自的name列表
*/
@Test
publicvoidgroupBySexName(){
result=people.stream().collect(
Collectors.groupingBy(
People::getSex,
Collectors.mapping(People::getName,Collectors.toSet())
));
}
}
以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持毛票票。