Java - como puedo extraer algo especifico de un array

// Gender.java

package com.jdojo.lambda;

public enum Gender {

MALE, FEMALE

}

// Person.java

package com.jdojo.lambda;

import java.time.LocalDate;

import java.util.ArrayList;

import java.util.List;

import static com.jdojo.lambda.Gender.MALE;

import static com.jdojo.lambda.Gender.FEMALE;

public class Person {

private String firstName;

private String lastName;

private LocalDate dob;

private Gender gender;

public Person(String firstName, String lastName, LocalDate dob, Gender gender) {

this.firstName = firstName;

this.lastName = lastName;

this.dob = dob;

this.gender = gender;

}

public String getFirstName() {

return firstName;

}

public void setFirstName(String firstName) {

this.firstName = firstName;

}

public String getLastName() {

return lastName;

}

public void setLastName(String lastName) {

this.lastName = lastName;

}

public LocalDate getDob() {

return dob;

}

public void setDob(LocalDate dob) {

this.dob = dob;

}

public Gender getGender() {

return gender;

}

public void setGender(Gender gender) {

this.gender = gender;

}

@Override

public String toString() {

return firstName + " " + lastName + ", " + gender + ", " + dob;

}

// A utility method

public static List<Person> getPersons() {

ArrayList<Person> list = new ArrayList<>();

list.add(new Person("John", "Jacobs", LocalDate.of(1975, 1, 20), MALE));

list.add(new Person("Wally", "Inman", LocalDate.of(1965, 9, 12), MALE));

list.add(new Person("Donna", "Jacobs", LocalDate.of(1970, 9, 12), FEMALE));

return list;

}

}

/ FunctionUtil.java

package com.jdojo.lambda;

import java.util.ArrayList;

import java.util.List;

import java.util.function.Consumer;

import java.util.function.Function;

import java.util.function.Predicate;

public class FunctionUtil {

// Applies an action on each item in a list

public static <T> void forEach(List<T> list, Consumer<? super T> action) {

for(T item : list) {

action.accept(item);

}

}

// Applies a filter to a list and returned the filtered list items

public static <T> List<T> filter(List<T> list, Predicate<? super T> predicate) {

List<T> filteredList = new ArrayList<>();

for(T item : list) {

if (predicate.test(item)) {

filteredList.add(item);

}

}

return filteredList;

}

// Maps each item in a list to a value

public static <T, R> List<R> map(List<T> list, Function<? super T, R> mapper) {

List<R> mappedList = new ArrayList<>();

for(T item : list) {

mappedList.add(mapper.apply(item));

}

return mappedList;

}

}

// FunctionUtilTest.java

package com.jdojo.lambda;

import static com.jdojo.lambda.Gender.MALE;

import java.util.List;

public class FunctionUtilTest {

public static void main(String[] args) {

List<Person> list = Person.getPersons();

// Use the forEach() method to print each person in the list

System.out.println("Original list of persons:");

FunctionUtil.forEach(list, p -> System.out.println(p));

// Filter only males

List<Person> maleList = FunctionUtil.filter(list, p -> p.getGender() == MALE);

System.out.println("\nMales only:");

FunctionUtil.forEach(maleList, p -> System.out.println(p));

// Map each person to his/her year of birth

List<Integer> dobYearList = FunctionUtil.map(list, p -> p.getDob().getYear());

System.out.println("\nPersons mapped to year of their birth:");

FunctionUtil.forEach(dobYearList, year -> System.out.println(year));

// Apply an action to each person in the list

// Add one year to each male's dob

FunctionUtil.forEach(maleList, p -> p.setDob(p.getDob().plusYears(1)));

System.out.println("\nMales only after ading 1 year to DOB:");

FunctionUtil.forEach(maleList, p -> System.out.println(p));

}

}