Lambdas

// Person class

public class Person {

    private String name;
    private float age;

    public Person(String name, float age) {
        this.name = name;
        this.age = age;
    }

    public String getName() {
        return name;
    }
}


//Foo class

import java.util.ArrayList;
import java.util.List;
import java.util.OptionalDouble;
import java.util.function.*;



    public static void main(String[] args) {
        Foo f = new Foo();
        Person p = new Person("Charlie", 19);
        Person p2 = new Person("Shawn", 22);
        Person p3 = new Person("Max", 35);
        Person p4 = new Person("Justin", 22);
        List<Person> names = new ArrayList<Person>();
        names.add(p);
        names.add(p2);
        names.add(p3);
        names.add(p4);

        OptionalDouble x = accept(names);
        System.out.println(x);
    }

    public static OptionalDouble accept(List<Person> names) {
        return names.stream().mapToInt(x -> x.getName().length()).average();
    }
}