利用google工具类实现对list集合分组

[code=plain] @org.junit.Test
public void testTest6() {
Person p1 = new Person("a",10,"男","china");
Person p2 = new Person("b",11,"女","japan");
Person p3 = new Person("c",12,"男","japan");
Person p4 = new Person("d",14,"男","USA");
Person p5 = new Person("e",14,"女","china");
List<Person> persons = new ArrayList<>();
persons.add(p1);
persons.add(p2);
persons.add(p3);
persons.add(p4);
persons.add(p5);
ImmutableSet digits = ImmutableSet.of(persons.toArray());
Function<Person, String> sex = new Function<Person, String>() {
@Override
public String apply(Person person) {
return person.getSex();
}
};
ImmutableListMultimap<String, Person> sexList = Multimaps.index(digits, sex);

ImmutableListMultimap ageList = Multimaps.index(digits, new Function<Person, Integer>() {
@Override
public Integer apply(Person person) {
return person.getAge();
}
});

ImmutableListMultimap countryList = Multimaps.index(digits, new Function<Person, String>() {
@Override
public String apply(Person person) {
return person.getContry();
}
});
System.out.println("按性别分组 = " + sexList);
System.out.println("按年龄分组 = " + ageList);
System.out.println("按国家分组 = " + countryList);

/** 结果
* 按性别分组 = {男=[Person@44d03877, Person@215750e4, Person@6b7fb9d5], 女=[Person@422b2fec, Person@e818616]}
* 按年龄分组 = {10=[Person@44d03877], 11=[Person@422b2fec], 12=[Person@215750e4], 14=[Person@6b7fb9d5, Person@e818616]}
* 按国家分组 = {china=[Person@44d03877, Person@e818616], japan=[Person@422b2fec, Person@215750e4], USA=[Person@6b7fb9d5]}
*/
//求性别为男的集合
System.out.println("sexList = " + sexList.get("男"));
//求年龄为14岁的集合
System.out.println("ageList = " + ageList.get(14));
//求国籍日本的集合
System.out.println("countryList = " + countryList.get("japan"));
/**
* 结果
* sexList = [Person@e818616, Person@789caeb2, Person@769165fa]
* ageList = [Person@769165fa, Person@43be3ce6]
* countryList = [Person@598a15ca, Person@789caeb2]
* 以上结果就是根据返回的map得到的集合数据。
* 可以把结果用List<Person> 保存。
* List<Person> personMan = sexList.get("男");
*/
}