如何检查txt文件是否包含字符串，如果不是，请不要复制它

Question

所以现在我在Minecraft中制作一个mod，它从服务器获取每个人的用户名并将其添加到txt文件，它可以工作，但问题是我不想复制名称当我再次使用该命令时。到目前为止，没有任何工作。如何检查txt是否已包含用户名，不要再次添加？谢谢。再次，我需要在将另一个名称写入列表之前，检查txt文件是否已包含名称，如果是，请不要添加它。

for (int i = 0; i < minecraft.thePlayer.sendQueue.playerInfoList.size(); i++) {
    List playerList = minecraft.thePlayer.sendQueue.playerInfoList;
    GuiPlayerInfo playerInfo = (GuiPlayerInfo) playerList.get(i);
    String playerName = StringUtils.stripControlCodes(playerInfo.name);

    try {
        fileWriter = new FileWriter(GameDirectory() + "\\scraped.txt", true);
        bufferedReader = new BufferedReader(new FileReader(GameDirectory() + "\\scraped.txt"));
        lineNumberReader = new LineNumberReader(new FileReader(GameDirectory() + "\\scraped.txt"));
    } catch (IOException e) {
        e.printStackTrace();
    }

    printWriter = new PrintWriter(fileWriter);

    try {
        fileWriter.write(playerName + "\r\n");
        lineNumberReader.skip(Long.MAX_VALUE);
    } catch (IOException e) {
        e.printStackTrace();
    }
    printWriter.flush();
}
addMessage("Scraped " + lineNumberReader.getLineNumber() + " usernames!");

编辑：真的需要答案的人:(谢谢

编辑：这就是我现在所拥有的，但它甚至不再写它了。

List playerList = minecraft.thePlayer.sendQueue.playerInfoList;

for (int i = 0; i < minecraft.thePlayer.sendQueue.playerInfoList.size(); i++) {
    GuiPlayerInfo playerInfo = (GuiPlayerInfo) playerList.get(i);
    String playerName = StringUtils.stripControlCodes(playerInfo.name);

    String lines;

    try {
        if ((lines = bufferedReader.readLine()) != null) {
            if (!lines.contains(playerName)) {
                bufferedWriter.write(playerName);
                bufferedWriter.newLine();
                bufferedWriter.flush();
            }
        }
    } catch (IOException e) {
        e.printStackTrace();
    }

}

int linenumber = 0;

try {
    while (lineNumberReader.readLine() != null) {
        linenumber++;
    }
} catch (IOException e) {
    e.printStackTrace();
}

Answer 1

你的第二段代码的逻辑是错误的。如果你写出它的伪代码，很容易理解为什么：

Open a File Reader at the start of the file

For every Player on the server
    Save the player name
    Read the next line of the file
        If we have not reached the end of the file
            If the player name is not on this line of the file
                Write the name of the player to the file

您需要阅读循环外的整个文件，然后检查播放器文件中是否存在，而不是恰好是与服务器上的播放器位置相同的行。

最简单的方法是在处理时将玩家保留在列表中，并将其读/写到文件中，如下所示：

public static List<String> loadPlayerList() throws FileNotFoundException
{
    final Scanner scanner = new Scanner(new File(GameDirectory() + "\\scraped.txt"));
    final List<String> players = new ArrayList<>();
    while(scanner.hasNextLine())
        players.add(scanner.nextLine());
    return players;
}

public static void writePlayersList(final List<String> players) throws IOException
{
    try(final BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(
            new FileOutputStream((GameDirectory() + "\\scraped.txt")))))
    {
        for(final String player : players)
        {
            writer.write(player);
            writer.newLine();
        }
    }
}

public static void main(String[] args) throws IOException
{
    final List<String> players = loadPlayerList();
    for(final GuiPlayerInfo player : minecraft.thePlayer.sendQueue.playerInfoList)
    {
        final String playerName = StringUtils.stripControlCodes(player.name);
        if(!players.contains(playerName))
            players.add(playerName);
    }
    writePlayersList(players);
}