从文件中获取行号

Question

如何实现一种方法来返回当前正在从文件中扫描的行的行号。我有两台扫描仪，一台用于文件（fileScanner），另一台用于线路（lineScanner）

这是我有的，但我不知道我是否需要构造函数中的行号！

public TextFileScanner(String fileName) throws FileNotFoundException
{
    this.fileScanner = new Scanner(new File(fileName));
    this.lineScanner = new Scanner(this.fileScanner.nextLine());
    this.lineNumber = 1;
}

我需要这个方法：

public int getLineNumber()
{

}

Answer 1

您可以只使用一个Scanner 对象来读取文件并报告行号。

这是一个示例代码：

import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;

public class LineNumber {

    public static void main(String [] args) throws FileNotFoundException {

        System.out.printf("Test!\n");

        File f = new File("test.txt");
        Scanner fileScanner = new Scanner(f);

        int lineNumber = 0;
        while(fileScanner.hasNextLine()){
            System.out.println(fileScanner.nextLine());
            lineNumber++;
        }

        fileScanner.close();
        System.out.printf("%d lines\n", lineNumber);

    }
}

现在，如果您想使用面向对象的编程方法执行此操作，那么您可以执行以下操作：

import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;

public class FileProcessor {

    // Mark these field as private so the object won't get tainted from outside
    private String fileName;
    private File file;

    /**
     * Instantiates an object from the FileProcessor class
     * 
     * @param fileName
     */
    public FileProcessor(String fileName) {
        this.fileName = fileName;
        this.file = new File(fileName);
    }

    public int getLineNumbers() {

        Scanner fileScanner = null;

        try {
            fileScanner = new Scanner(this.file);
        } catch (FileNotFoundException e) {
            System.out.printf("The file %s could not be found.\n",
                    this.file.getName());
        }

        int lines = 0;

        while (fileScanner.hasNextLine()) {
            lines++;
            // Go to next line in file
            fileScanner.nextLine();
        }

        fileScanner.close();

        return lines;
    }

    /**
     * Test our FileProcessor Class
     * 
     * @param args
     * @throws FileNotFoundException
     */

    public static void main(String[] args) throws FileNotFoundException {

        FileProcessor fileProcessor = new FileProcessor("text.txt");
        System.out.printf("%d lines\n", fileProcessor.getLineNumbers());
    }
}

Answer 2

打印当前行号：

System.out.println("行号为" + new Exception().getStackTrace()[0].getLineNumber());

例子：

公共类 LineNumberTest{

 public static void main(String []args){
    System.out.println("The line number is " + new Exception().getStackTrace()[0].getLineNumber());
 }

}