java BufferedReader类 mark()方法的奇怪表现

Question

使用I/o包的BufferedReader 类的mark()方法，遇到了奇怪的情况，就是有时在mark(0)填入0，有些代码能正常表现，有些不能正常。代码如下：

import java.io.*;

class test {
    public static void main(String[] args) throws IOException {

        try(
        BufferedReader r = new BufferedReader(new StringReader(
                "Happy Birthday to You!\n" +
                        "Happy Birthday, dear " + System.getProperty("user.name") + "!"));)
        {
            if(r.markSupported()) {
                r.mark(0); // save the data we are about to read
                System.out.println(r.readLine()); // read the first line
                r.reset(); // jump back to the marked position
                //r.mark(1000); // start saving the data again
                System.out.println(r.readLine()); // read the first line again
                System.out.println(r.readLine()); // read the second line
                r.reset(); // jump back to the marked position
                System.out.println(r.readLine()); // read the first line one final
            }
            }catch (IOException e){
             System.out.println(e);
        }
    }
}

运行出现
Happy Birthday to You!
java.io.IOException: Mark invalid

import java.io.*;
import static java.lang.System.out;

public class App {

    public static final String TEST_STR = "Line 111111111111111111\nLine 222222222222222222\nLine 33333333333333333333333\nLine 4444444444444444444444\n";

    public static void main(String[] args) {

        try (BufferedReader in = new BufferedReader(new StringReader(TEST_STR))) {

            // first check if this Reader support mark operation
            if (in.markSupported()) {

                out.println(in.readLine());
                in.mark(0);                     // mark 'Line 2'
                out.println(in.readLine());
                out.println(in.readLine());
                in.reset();                     // reset 'Line 2'
                out.println(in.readLine());
                in.reset();                     // reset 'Line 2'
                out.println(in.readLine());
                in.mark(0);                     // mark 'Line 3'
                out.println(in.readLine());
                in.reset();                     // reset 'Line 3'
                out.println(in.readLine());
                out.println(in.readLine());
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

运行没有问题。
Line 111111111111111111
Line 222222222222222222
Line 33333333333333333333333
Line 222222222222222222
Line 222222222222222222
Line 33333333333333333333333
Line 33333333333333333333333
Line 4444444444444444444444

运行在intellij idea上。
请各位大侠指出那个地方出问题了。