Java Average age by gender in Stream

Description

Demo Code

import java.time.LocalDate;
import java.time.chrono.IsoChronology;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;


public class BulkDataOperationsExamples {

    public static void main(String... args) {
        /*w  w w  .j  ava2s  .  c  om*/
        // Create sample data
    
        List<Person> roster = Person.createRoster();
        // 1. Print names of members, for-each loop
            
        System.out.println("Members of the collection (for-each loop):");
        for (Person p : roster) {
            System.out.println(p.getName());
        }

            
        // 9. Average age by gender
             
        System.out.println("Average age by gender:");
        Map<Person.Sex, Double> averageAgeByGender =
            roster
                .stream()
                .collect(
                     Collectors.groupingBy(
                         Person::getGender,                      
                         Collectors.averagingInt(Person::getAge)));
                     
        for (Map.Entry<Person.Sex, Double> e : averageAgeByGender.entrySet()) {
            System.out.println(e.getKey() + ": " + e.getValue());
        }
             
            
    }
}


class Person {

    public enum Sex {
        MALE, FEMALE
    }

    String name;
    LocalDate birthday;
    Sex gender;
    String emailAddress;

    Person(String nameArg, LocalDate birthdayArg, Sex genderArg,
            String emailArg) {
        name = nameArg;
        birthday = birthdayArg;
        gender = genderArg;
        emailAddress = emailArg;
    }

    public int getAge() {
        return birthday.until(IsoChronology.INSTANCE.dateNow()).getYears();
    }

    public void printPerson() {
        System.out.println(name + ", " + this.getAge());
    }

    public Sex getGender() {
        return gender;
    }

    public String getName() {
        return name;
    }

    public String getEmailAddress() {
        return emailAddress;
    }

    public LocalDate getBirthday() {
        return birthday;
    }

    public static int compareByAge(Person a, Person b) {
        return a.birthday.compareTo(b.birthday);
    }

    public static List<Person> createRoster() {

        List<Person> roster = new ArrayList<>();
        roster.add(new Person("Fred", IsoChronology.INSTANCE.date(1980, 6,
                20), Person.Sex.MALE, "fred@example.com"));
        roster.add(new Person("Jane", IsoChronology.INSTANCE.date(1990, 7,
                15), Person.Sex.FEMALE, "jane@example.com"));
        roster.add(new Person("George", IsoChronology.INSTANCE.date(1991,
                8, 13), Person.Sex.MALE, "george@example.com"));
        roster.add(new Person("Bob", IsoChronology.INSTANCE.date(2000, 9,
                12), Person.Sex.MALE, "bob@example.com"));

        return roster;
    }

}
/*
 * Copyright (c) 2013, Oracle and/or its affiliates. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 *   - Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *
 *   - Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 *
 *   - Neither the name of Oracle or the names of its
 *     contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
Java Average age by gender in Stream - Java Lambda Stream

Description

Demo Code

Result

Related Tutorials
