Java String.startsWith() "seems"不适用于文本文件的第一行

Question

我有一个像这样的文本文件，我想解析该文本文件中的信息。

#title キミと☆Are You Ready？
#artist トライクロニカ
#mobile deresimu
#easy 0
#normal 22
#hard 27
#tag SHOW BY ROCK!!
#preset all

我用这段代码来解析它。

File infoFile = new File(dir, "info.txt");
//parse info.txt
String songName="?";
String artist = "?";
int difficulties[] = new int[5];

try {
    BufferedReader br = new BufferedReader(new FileReader(infoFile));
    String line = br.readLine();
    while (line != null) {
        Log.v(TAG, "line=" + line);
        //I hate BOM!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
        /*
        <a href="http://www.faqs.org/rfcs/rfc3629.html">RFC 3629 - UTF-8, a transformation format of ISO 10646</a>
        *
        * <p>The
         * <a href="http://www.unicode.org/unicode/faq/utf_bom.html">Unicode FAQ</a>
    * defines 5 types of BOMs:<ul>
        * <li><pre>00 00 FE FF  = UTF-32, big-endian</pre></li>
        * <li><pre>FF FE 00 00  = UTF-32, little-endian</pre></li>
         * <li><pre>FE FF        = UTF-16, big-endian</pre></li>
        * <li><pre>FF FE        = UTF-16, little-endian</pre></li>
         * <li><pre>EF BB BF     = UTF-8</pre></li>
        * </ul></p>
        *
        * https://stackoverflow.com/questions/1835430/byte-order-mark-screws-up-file-reading-in-java
         */
        line=line.replace("\u00EF\u00BB\u00BF", "");
        line=line.replace("\u0000 \u0000 \u00FE \u00FF","");
        line=line.replace("\u00FF \u00FE \u0000 \u0000","");
        line=line.replace("\u00FE \u00FF","");
        line=line.replace("\u00FF \u00FE","");
        if (line.startsWith("#title")) {
            Log.v(TAG, "startswith");
            line = line.replace("#title ", "").trim();
            songName = line;
        } else if (line.startsWith("#artist")) {
            line = line.replace("#artist ", "").trim();
            artist = line;
        } else if (line.startsWith("#easy")) {
            difficulties[0] = Integer.parseInt(line.replace("#easy ", "").trim());

        } else if (line.startsWith("#normal")) {
            difficulties[1] = Integer.parseInt(line.replace("#normal ", "").trim());

        } else if (line.startsWith("#hard")) {
            difficulties[2] = Integer.parseInt(line.replace("#hard ", "").trim());
        } else if (line.startsWith("#master")) {
            difficulties[3] = Integer.parseInt(line.replace("#master ", "").trim());
        } else if (line.startsWith("#apex")) {
            difficulties[4] = Integer.parseInt(line.replace("#apex ", "").trim());
            continue;
        }
        line = br.readLine();
    }
} catch (IOException | NumberFormatException e) {
    throw new RuntimeException(e);
}
//info.txt parse done.
Log.v(TAG, "Info.txt parse done.");
Log.v(TAG, "Song name=" + songName);
Log.v(TAG, "Difficulties=" + Arrays.toString(difficulties));
Log.v(TAG, "Artist=" + artist);
Log.v(TAG, "Folder=" + dir.getName());

解析除第一行之外的所有其他行都可以。 if (line.startsWith("#title")) { 对于给定的文本文件似乎永远不会成立。当我将 startsWith 更改为 contains 时，它起作用了。

首先我认为这是一个BOM问题，所以我添加了5行删除BOM序列。然而它没有用。变量 songName 始终为“?”当我在第一行使用 startsWith 时。

有任何线索说明为什么此代码无法匹配 #title 吗？ 谢谢。

Logcat 输出:

2019-03-10 23:00:22.872 23600-23600/sma.rhythmtapper V/NoteFile: line=#title キミと☆Are You Ready？
2019-03-10 23:00:22.872 23600-23600/sma.rhythmtapper V/NoteFile: line=#artist トライクロニカ
2019-03-10 23:00:22.872 23600-23600/sma.rhythmtapper V/NoteFile: line=#mobile deresimu
2019-03-10 23:00:22.873 23600-23600/sma.rhythmtapper V/NoteFile: line=#easy 0
2019-03-10 23:00:22.873 23600-23600/sma.rhythmtapper V/NoteFile: line=#normal 22
2019-03-10 23:00:22.873 23600-23600/sma.rhythmtapper V/NoteFile: line=#hard 27
2019-03-10 23:00:22.874 23600-23600/sma.rhythmtapper V/NoteFile: line=#tag SHOW BY ROCK!!
2019-03-10 23:00:22.876 23600-23600/sma.rhythmtapper V/NoteFile: line=#preset all
2019-03-10 23:00:22.876 23600-23600/sma.rhythmtapper V/NoteFile: Info.txt parse done.
2019-03-10 23:00:22.876 23600-23600/sma.rhythmtapper V/NoteFile: Song name=?
2019-03-10 23:00:22.877 23600-23600/sma.rhythmtapper V/NoteFile: Difficulties=[0, 22, 27, 0, 0]
2019-03-10 23:00:22.877 23600-23600/sma.rhythmtapper V/NoteFile: Artist=トライクロニカ
2019-03-10 23:00:22.877 23600-23600/sma.rhythmtapper V/NoteFile: Folder=キミと☆Are You Ready？

编辑

我通过将字节序列打印到logcat来定位问题。它说:

"#title キミと☆准备好了吗？"-> [-17, -69, -65, 35, 116, 105, 116, 108, 101, 32, -29, -126, -83, - 29、-125、-97、-29、-127、-88、-30、-104、-122、65、114、101、32、89、111、117、32、82、101、97、100、 121、-17、-68、-97]

“#title”-> [35, 116, 105, 116, 108, 101]

所以我需要从 line 变量中删除 -17、-69、-65。在不使用外部库的情况下如何实现目标？

Answer 1

对 BOM 导致问题的怀疑是正确的。

另外，我将 BOM 删除代码更改为:

line=line.replace("\uEFBB\u00BF", "");
line=line.replace("\u0000\uFEFF","");
line=line.replace("\uFFFE\u0000","");
line=line.replace("\uFEFF","");
line=line.replace("\uFFFE","");

小心

• 空白
• \u00EF != 字节 0xEF

感谢所有试图帮助我的人，并希望其他可能遇到同样问题的人从这篇文章中得到帮助。