java8分组求和_java8实现分组求和，平均等数据统计java8 实现分组聚合，平均等数据统计
写在前⾯
⼀、分组实现
1.1、简单分组
Map departmentNames = departmentDbs.stream()
.Map(
Department::getDepartmentName,
Department::getDepartmentId)
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1.2、集合分组
stone是什么意思/**
fatal* 分组函数使⽤
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glivec* 这个⽰例返回，分组后的集合对象
*/
发挥英语>cav@Test
telephone
public void t12_2() {
List roster = Arrays.asList(
new Person("as", w(), Person.Sex.FEMALE,"Test@",12),
new Person("zx", w(), Person.Sex.FEMALE,"Test@",12),
new Person("zc", w(), Person.Sex.MALE,"Test@",12),
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new Person("zv", w(), Person.Sex.FEMALE,"Test@",12),
new Person("zb", w(), Person.Sex.MALE,"Test@",12),
new Person("zn", w(), Person.Sex.FEMAL
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