The Streams API supports different types of find operations on stream elements.
The following methods in the Stream interface are used to perform find operations:
Optional<T> findAny() Optional<T> findFirst()
The primitive type streams such as IntStream, LongStream, and DoubleStream also contain the same methods that work with a predicate and an optional one for primitive types.
All find operations are terminal operations. They are also short-circuiting operations. A short-circuiting operation may not have to process the entire stream to return the result.
The following code shows how to perform find operations on streams.
import java.time.LocalDate; import java.time.Month; import java.util.Arrays; import java.util.List; import java.util.Optional; /*w w w .j a v a 2s. co m*/ public class Main { public static void main(String[] args) { List<Employee> persons = Employee.persons(); // Find any male Optional<Employee> anyMale = persons.stream().filter(Employee::isMale).findAny(); if (anyMale.isPresent()) { System.out.println("Any male: " + anyMale.get()); } else { System.out.println("No male found."); } // Find the first male Optional<Employee> firstMale = persons.stream().filter(Employee::isMale).findFirst(); if (firstMale.isPresent()) { System.out.println("First male: " + anyMale.get()); } else { System.out.println("No male found."); } } } 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; } }
The code above generates the following result.