构造java.util.Scanner的意外行为

我有以下文件 lines.txt

Line1
Line2
Line3

我正在使用扫描仪逐行解析此文件的内容。我在 LinesReader.java 中有以下设置

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;

class Line {
    Line(String content) {
        this.content = content;
    }
    public String content;

    public String toString() {
        return content;
    }
}

public class LinesReader {
    public static Line buildLine(InputStream is) {
        Scanner scanner = new Scanner(is);
        if (scanner.hasNextLine()) {
            return new Line(scanner.nextLine());
        }
        return null;
    }
    public static Line buildLine(Scanner scanner) {
        if (scanner.hasNextLine()) {
            return new Line(scanner.nextLine());
        }
        return null;
    }

    public static void main(String[] args) throws FileNotFoundException {
        List<Line> lines = new ArrayList<>();
        Line line = null;
        FileInputStream is = new FileInputStream("lines.txt");
        // buildLine(scanner) works as expected
        while ((line = buildLine(is)) != null) {
            lines.add(line);
        }

        System.err.println(lines);
    }
}

输出是

[Line1]

预期的输出将是

[Line1, Line2, Line3]

我了解 Scanner 实现了 AutoCloseable，但根据仅适用于try-with-resources构造而不适用于
此处的文档。另外，当我调试时，它说底层流​​是打开的。第二次调用scanner.hasNextLine()意外失败。