Collectors partitioningBy(Predicate<? super T> predicate)
returns a Collector which partitions the input elements according to a Predicate,
and organizes them into a Map<Boolean, List<T>>.
partitioningBy
has the following syntax.
public static <T> Collector<T,?,Map<Boolean,List<T>>> partitioningBy(Predicate<? super T> predicate)
The following example shows how to use partitioningBy
.
import java.time.LocalDate; import java.time.Month; import java.util.Arrays; import java.util.List; import java.util.Map; import java.util.stream.Collectors; public class Main { public static void main(String[] args) { Map<Boolean, List<Employee>> partionedByMaleGender = Employee.persons()// ww w . j a v a2 s.c om .stream() .collect(Collectors.partitioningBy(Employee::isMale)); System.out.println(partionedByMaleGender); } } class Employee { public static enum Gender { MALE, FEMALE } private long id; private String name; private Gender gender; private LocalDate dob; private double income; public Employee(long id, String name, Gender gender, LocalDate dob, double income) { this.id = id; this.name = name; this.gender = gender; this.dob = dob; this.income = income; } public boolean isMale() { return this.gender == Gender.MALE; } public static List<Employee> persons() { Employee p1 = new Employee(1, "Jake", Gender.MALE, LocalDate.of(1971, Month.JANUARY, 1), 2343.0); Employee p2 = new Employee(2, "Jack", Gender.MALE, LocalDate.of(1972, Month.JULY, 21), 7100.0); Employee p3 = new Employee(3, "Jane", Gender.FEMALE, LocalDate.of(1973, Month.MAY, 29), 5455.0); Employee p4 = new Employee(4, "Jode", Gender.MALE, LocalDate.of(1974, Month.OCTOBER, 16), 1800.0); Employee p5 = new Employee(5, "Jeny", Gender.FEMALE, LocalDate.of(1975, Month.DECEMBER, 13), 1234.0); Employee p6 = new Employee(6, "Jason", Gender.MALE, LocalDate.of(1976, Month.JUNE, 9), 3211.0); List<Employee> persons = Arrays.asList(p1, p2, p3, p4, p5, p6); return persons; } @Override public String toString() { String str = String.format("(%s, %s, %s, %s, %.2f)\n", id, name, gender, dob, income); return str; } }
The code above generates the following result.