Java 从给定的文本文件中提取带有空格的字母表，而不在文件中包含哨兵

我有两个文本文件：

1

Extract\u tweet.txt

-文件格式为

user\u id tweet\u text

12163922    5407952300  I think I just discovered the hour when the office thermostat changes. And it ain't a good time to be at work...brrrr   2009-11-03 19:22:54

2

locations.txt

-下面数据中的相关性是第3列，其作用类似于搜索字符串

asciiname: name of geographical point in plain ascii characters, varchar(200)

4045431 Point Poker Point Poker     52.89508    173.29911   T   CAPE    US      AK  016         0       9   America/Adak    2013-10-26

我想从这些文件中提取一些数据。数据通常只能是a-z、a-z和任何空格。我之前考虑过将字符串标记化。然而，由于没有给出sentinal，我想到了使用正则表达式。PFB提取27个字符的代码段，即a-Z或a-Z或任何空格。我只想提取小写文本，即如果有大写字符，则应将其转换为小写

我将打开文件1-

Extract_tweet.txt

，并将完整文本作为单个字符串。然后我尝试用null替换每个非字母字符

   public void readfromFile() throws FileNotFoundException
    {
        Scanner inputStream;
        String source=null;
        FileInputStream file = new FileInputStream("Extract_tweet.txt");    
        inputStream = new Scanner(file);
        while(inputStream.hasNextLine())    //Read from file till the last line of the file.
        {
            source = inputStream.nextLine();
            System.out.println(source);
            replaceAll(source);

        }
        inputStream.close();
    }
    public String replaceAll(String source) 
    {
        String regex = "[A-Z]*"+"["+source.toLowerCase()+"|"+"[a-z]*"+"[\\s]";
        source = source.replaceAll(regex, "");
        System.out.println(source);
        return source;
    }

    public static void main(String[] args) {

        StringProcessing sp = new StringProcessing();
        try {
            sp.readfromFile();
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

    }

一旦我运行这个代码，我的错误率就会降低

60730027    6320951896  @thediscovietnam coo.  thanks. just dropped you a line. 2009-12-03 18:41:07
Exception in thread "main" java.util.regex.PatternSyntaxException: Illegal character range near index 88
[A-Z]*[60730027 6320951896  @thediscovietnam coo.  thanks. just dropped you a line. 2009-12-03 18:41:07|[a-z]*[\s]

---

请像那样换线

String regex = "[A-Z]* |"+"[a-z]*"+"[\\s]";

它会很好用的

我做了一些改变。但是，我想将大写改为小写，并用null替换所有字母数字值

   public void readfromFile() throws FileNotFoundException
    {
        Scanner inputStream;
        String source=null;
        FileInputStream file = new FileInputStream("Extract_tweet.txt");    
        inputStream = new Scanner(file);
        while(inputStream.hasNextLine())    //Read from file till the last line of the file.
        {
            source = inputStream.nextLine();
            System.out.println(source);
            replaceAll(source);

        }
        inputStream.close();
    }
    public String replaceAll(String source) 
    {
        String regex = "[A-Z]*"+"["+source.toLowerCase()+"|"+"[a-z]*"+"[\\s]";
        source = source.replaceAll(regex, "");
        System.out.println(source);
        return source;
    }

    public static void main(String[] args) {

        StringProcessing sp = new StringProcessing();
        try {
            sp.readfromFile();
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

    }

展开您的方法：

public String replaceAll(String source) throws FileNotFoundException {
    String regex = "[A-Z]* |[a-z]*\\s";
    source = source.replaceAll(regex, "")
                   .replaceAll("\\d", "")
                   .toLowerCase();

    System.out.println(source);
    writetoFile(source);
    return source;
}

---

是的，至少它起作用了。但是，我希望删除所有字母数字值，并希望将大写值转换为小写值。有什么建议吗？请用例子简单解释一下。欢迎来到堆栈溢出。请坐一会儿。