Calculate average age of male
members
import java.time.LocalDate;
import java.time.chrono.IsoChronology;
import java.util.ArrayList;
import java.util.List;
public class Main
{
public static void main(String[] args)
{
List roster = createRoster();
double average = roster
.stream()
.filter(p -> p.getGender() == Person.Sex.Male)
.mapToInt(Person::getAge)
.average()
.getAsDouble();
System.out.println("Average age (bulk data operations): " +average);
}
public static List createRoster()
{
List roster = new ArrayList<>();
roster.add(
new Person(
"Fred",
IsoChronology.Instance.date(1980, 6, 20),
Person.Sex.Male,
"fredexample"));
roster.add(
new Person(
"Jane",
IsoChronology.Instance.date(1990, 7, 15),
Person.Sex.Female, "janeexample"));
roster.add(
new Person(
"George",
IsoChronology.Instance.date(1991, 8, 13),
Person.Sex.Male, "georgeexample "));
roster.add(
new Person(
"Bob",
IsoChronology.Instance.date(2000, 9, 12),
Person.Sex.Male, "bobexample"));
return roster;
}
}
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);
}
}
Get Average age by gender
import java.time.LocalDate;
import java.time.chrono.IsoChronology;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.function.IntConsumer;
import java.util.stream.Collectors;
public class Main
{
public static void main(String[] args)
{
List roster = createRoster();
System.out.println("Average age by gender:");
Map averageAgeByGender =
roster
.stream()
.collect(
Collectors.groupingBy(
Person::getGender,
Collectors.averagingInt(Person::getAge)));
for (Map.Entry e : averageAgeByGender.entrySet())
{
System.out.println(e.getKey() + ": " + e.getValue());
}
}
public static List createRoster()
{
List roster = new ArrayList<>();
roster.add(
new Person(
"Fred",
IsoChronology.Instance.date(1980, 6, 20),
Person.Sex.Male,
"fredexample "));
roster.add(
new Person(
"Jane",
IsoChronology.Instance.date(1990, 7, 15),
Person.Sex.Female, "janeexample"));
roster.add(
new Person(
"George",
IsoChronology.Instance.date(1991, 8, 13),
Person.Sex.Male, "georgeexample "));
roster.add(
new Person(
"Bob",
IsoChronology.Instance.date(2000, 9, 12),
Person.Sex.Male, "bobexample"));
return roster;
}
}
class Averager implements IntConsumer
{
private int total = 0;
private int count = 0;
public double average()
{
return count > 0 ? ((double) total)/count : 0;
}
public void accept(int i) { total += i; count++; }
public void combine(Averager other)
{
total += other.total;
count += other.count;
}
}
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);
}
}
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