在Java流中实现for循环for数组列表？

Question

问题：我能否使用Java流API（即一行）实现方法private void fillingArrayList()。需要变量i来定义字符串的长度；我尝试为每个循环，但它不工作。我需要一个循环的范围。

import org.apache.commons.lang3.StringUtils;

public class Tolls {
    public static String digitsConcatenation(short number, long times) {
        return StringUtils.repeat(Character.forDigit(number, 10), Long.valueOf(times).intValue());
    }
}

public class Progression {
    public Progression(Digit digit) {
        this.digit = digit;
        this.numbers = new ArrayList<>(Long.valueOf(digit.getTimes()).intValue());
        this.fillingArrayList();
    }

    public Optional<Long> getProgressionSum() {
        return this.numbers.stream().reduce(Long::sum);
    }


    public List<Long> getNumbers() {
        return Collections.unmodifiableList(this.numbers);
    }

    private void fillingArrayList() {
        for (int i = 1; i <= digit.getTimes(); i++)
            this.numbers.add(Long.valueOf(Tolls.digitsConcatenation(digit.getNumber(), i)));
    }

    private final List<Long> numbers;
    private final Digit digit;
}

我的尝试：

 private void fillingArrayList() {
        Arrays.stream(this.numbers.toArray())
                .forEach(i-> this.numbers.add(
                        Long.valueOf(Tolls.digitsConcatenation(
                                digit.getNumber(), (Long) i))));
        
    }

Answer 1

以下应起作用：

  IntStream.rangeClosed(1, digit.getTimes()).forEach(i -> this.numbers.add(Long.valueOf(Tolls.digitsConcatenation(digit.getNumber(), i))););