java - 我如何使用trim()方法来完成这项工作？我需要读取txt文件，同时忽略空白行和以 "//"开头的行

Question

public void readToooooolData(String fileName) throws FileNotFoundException
    {
         File dataFile = new File(fileName);
        Scanner scanner = new Scanner(dataFile);
        scanner.useDelimiter("( *, *)|(\\s*,\\s*)|(\r\n)|(\n)");

         while(scanner.hasNextLine()) {
             String line = scanner.nextLine();
        if(!line.startsWith("//") || !(scanner.nextLine().startsWith(" ") )) {
          String toolName = scanner.next();
         String itemCode = scanner.next();
         int timesBorrowed = scanner.nextInt();
         boolean onLoan = scanner.nextBoolean();
         int cost = scanner.nextInt();
         int weight = scanner.nextInt();
         storeTool( new Tool(toolName, itemCode, timesBorrowed, onLoan, cost, weight) );
         scanner.nextLine();
        } 
        scanner.close();

    }

}

txt 文件:

// this is a comment, any lines that start with //
// (and blank lines) should be ignored

// data is toolName, toolCode, timesBorrowed, onLoan, cost, weight  
Makita BHP452RFWX,RD2001, 12 ,false,14995,1800  
Flex Impact Screwdriver FIS439,RD2834,14,true,13499,1200  
DeWalt D23650-GB Circular Saw, RD6582,54,true,14997,5400  
Milwaukee DD2-160XE Diamond Core Drill,RD4734,50,false,38894,9000  
Bosch GSR10.8-Li Drill Driver,RD3021,25, true,9995,820  
 Bosch GSB19-2REA Percussion Drill,RD8654,85,false,19999,4567  
Flex Impact Screwdriver FIS439, RD2835,14,false,13499,1200  
DeWalt DW936 Circular Saw,RD4352,18,false,19999,3300  
Sparky FK652 Wall Chaser,RD7625,15,false,29994,8400  

Answer 1

您的代码存在一些问题。

• 最好使用 try with resources打开扫描仪

• 您指定的某些分隔符是重复的，有些是不必要的。空间包含在 \s 中，所以(\s*,\s*)是 ( *, *) 的重复项，和(\r\n)|(\n)不需要。

• 您从文件中读取一行并测试是否为注释或空行 - 好的。然后你需要从已经读取的行中提取 token ，但你不能使用 scanner.next()为此，因为它会在您刚刚阅读的行之后检索下一个标记。因此，您的代码实际上所做的是尝试解析非注释/非空行之后行上的信息。

• 还有另一个scanner.nextLine()在循环末尾，因此您可以从文件中再跳过一行。

public void readToooooolData(String fileName) throws FileNotFoundException {
    File dataFile = new File(fileName);
    try (Scanner scanner = new Scanner(dataFile)) {
      while (scanner.hasNextLine()) {
        String line = scanner.nextLine().trim();
        if (line.startsWith("//") || line.isEmpty()) {
          continue;
        }
        String tokens[] = line.split("\\s*,\\s*");
        if (tokens.length != 6) {
          throw new RuntimeException("Wrong data file format");
        }
        String toolName = tokens[0];
        String itemCode = tokens[1];
        int timesBorrowed = Integer.parseInt(tokens[2]);
        boolean onLoan = Boolean.parseBoolean(tokens[3]);
        int cost = Integer.parseInt(tokens[4]);
        int weight = Integer.parseInt(tokens[5]);
        storeTool( new Tool(toolName, itemCode, timesBorrowed, onLoan, cost, weight) );
      }
    }
  }