Lambda表达式初始化数组

Question

有没有办法使用简单的lambda表达式初始化数组或集合？

就像是

// What about this?
Person[] persons = new Person[15];
persons = () -> {return new Person()};

要么

// I know, you need to say how many objects
ArrayList<Person> persons = () -> {return new Person()};

Answer 1

当然 - 我不知道它有多有用,但它肯定是可行的:

import java.util.*;
import java.util.function.*;
import java.util.stream.*;

public class Test
{
    public static void main(String[] args)
    {
        Supplier<Test> supplier = () -> new Test();
        List<Test> list = Stream
            .generate(supplier)
            .limit(10)
            .collect(Collectors.toList());
        System.out.println(list.size()); // 10
        // Prints false, showing it really is calling the supplier
        // once per iteration.
        System.out.println(list.get(0) == list.get(1));
    }
}

Answer 2

如果您已经有预先分配的数组,则可以使用lambda表达式使用Arrays.setAll或填充它Arrays.parallelSetAll:

Arrays.setAll(persons, i -> new Person()); // i is the array index

要创建新阵列,您可以使用

Person[] persons = IntStream.range(0, 15)  // 15 is the size
    .mapToObj(i -> new Person())
    .toArray(Person[]::new);