从 java 8 流中获取 N(3) 个列表（基于 ENUM 性别）并根据 ENUM 过滤条件

Question

如何根据性别枚举类型创建 N 个列表？如果我有 3 个可能的 GENDER 枚举（男性、女性、其他），我需要 3 个列表。如何使用 java 8 流 API 实现此目的？

在这种情况下，我需要像带有 3 个键的 MAP 之类的东西。genderMap.get(GENDER.male)。

Map<GENDER, List<Person>> genderMap;

尝试使用 partitioningBy

Map<Boolean, List<Person>> genderMap= people.stream().collect(Collectors.partitioningBy(malePredicate()));

System.out.println("MALE "+genderMap.get(true));

System.out.println("FEMALE "+genderMap.get(false));

private static Predicate<Person> malePredicate(){

    return p ->  p.getGender() != null && p.getGender().equalsIgnoreCase("male");

}

private static Predicate<Person> femalePredicate(){

    return p ->  p.getGender() != null && p.getGender().equalsIgnoreCase("female");

}

MALE [Person [id=1, name=SAMPLE_1, age=11, gender=male, sal=100, monthlyExpenseAmount=120.00], Person [id=2, name=SAMPLE_2, age=12, gender=male, sal=100 , monthlyExpenseAmount=120.00]]

FEMALE [Person [id=0, name=SAMPLE_0, age=10, gender=other, sal=100, monthlyExpenseAmount=120.00], Person [id=3, name=SAMPLE_3, age=13, gender=female, sal=100 , monthlyExpenseAmount=100.00], 人 [id=4, name=SAMPLE_4, age=14, gender=female, sal=100, monthlyExpenseAmount=100.00], Person [id=5, name=SAMPLE_5, age=15, gender=female , sal=100, monthlyExpenseAmount=100.00]]

Answer 1

使用groupingBy()和toList()：Map<Gender,&nbsp;List<Person>>&nbsp;genderMap&nbsp;=&nbsp;people.stream() &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;.collect(Collectors.groupingBy(Person::getGender,&nbsp;Collectors.toList()));演示见IDEONE 。

Answer 2

.partitioningBy()用于将结果分成 2 组。你在找.groupingBy()Map<Gender,&nbsp;List<Person>>&nbsp;genderMap&nbsp;=&nbsp;people.stream() &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;.collect(Collectors.groupingBy(Person::getGender));