java - 使用 OpenCSV 获取列数

Question

我有一个 txt 文件，我想计算列数。 (我用的是openCSV)

public class demoTable {
    public demoTable(){
         read();
        JOptionPane.showMessageDialog(null, "number of columns inside file: " + getNumberOfColumnsFromFile(), null, JOptionPane.INFORMATION_MESSAGE);
    close();
    }

    private void read(){
    try {
        this.fileInputStream = new FileInputStream("D:\\Book3.txt");
        UTF8_CHARSET = StandardCharsets.UTF_8.newDecoder();
        UTF8_CHARSET.onMalformedInput(CodingErrorAction.REPLACE);
        this.fileReader = new InputStreamReader(this.fileInputStream, UTF8_CHARSET);
        this.reader = new CSVReader(this.fileReader, '\t');
    } 
    catch (FileNotFoundException ex) {
        Logger.getLogger(VJTable.class.getName()).log(Level.SEVERE, null, ex);
    }
    }

    private int getNumberOfColumnsFromFile(){
    //Estimating number of rows from file (Googled that).
    this.numberOfColumns = 0;
    try {
        while( (this.nextLine = this.reader.readNext()) != null){
            this.numberOfColumns++;
        }
    } 
    catch (IOException ex) {
        Logger.getLogger(VJTable.class.getName()).log(Level.SEVERE, null, ex);
    }
    return this.numberOfColumns;
   }

   private void close(){
    try {
        this.fileInputStream.close();
        this.fileReader.close();
        this.reader.close();
    }
    catch (IOException ex) {
        Logger.getLogger(VJTable.class.getName()).log(Level.SEVERE, null, ex);
    }
    }
}

不幸的是，getNumberOfColumnsFromFile() 方法返回行数而不是列数。你能告诉我我在这里做的不好吗？提前谢谢你。

Answer 1

CSVRearder.readNext()方法返回一个 String[]，其中每个列/值都是一个元素:

Reads the next line from the buffer and converts to a string array [..] with each comma-separated element as a separate entry.

因此，

String[] header = this.reader.readNext(); // assuming first read
if (header != null) {                     // and there is a (header) line
   int columnCount = header.length;       // get the column count
}