Java 中的 LineNumberReader

LineNumberReader 是一个缓冲的字符输入流，用于跟踪行号。说人话就是一个用于逐行读取文件的工具类

它提供了方法 setLineNumber() 和 getLineNumber()，分别用于设置和获取当前行号。

Java 使用例

file.txt

Hello Friends! 
This is an example of LineNumberReader 
LineNumberReader is a subclass of BufferedReader 

import java.io.File;
import java.io.FileReader;
import java.io.IOException;
import java.io.LineNumberReader;

public class LineNumberReaderExample {

  public static void main(String[] args) {
    File file = new File("file.txt");
    FileReader fileReader = null;
    LineNumberReader lineNumberReader = null;
    try {
      fileReader = new FileReader(file);
      lineNumberReader = new LineNumberReader(fileReader);

      // Get Line Number
      int lineNum = lineNumberReader.getLineNumber();
      System.out.println("Line number : " + lineNum);

      // Set Line Number
      lineNumberReader.setLineNumber(2);

      // Get Line Number
      lineNum = lineNumberReader.getLineNumber();
      System.out.println("Line number : " + lineNum);

      String line = null;
      while ((line = lineNumberReader.readLine()) != null) {
        System.out.println(line);
      }

      // Get Line Number
      lineNum = lineNumberReader.getLineNumber();
      System.out.println("Line number : " + lineNum);
    } catch (IOException e) {
      e.printStackTrace();
    } finally {
      try {
        if (fileReader != null) {
          fileReader.close();
        }
        if (lineNumberReader != null) {
          lineNumberReader.close();
        }
      } catch (Exception e) {
        e.printStackTrace();
      }
    }
  }
}

输出：

Line number : 0 
Line number : 2 
Hello Friends! 
This is an example of LineNumberReader 
LineNumberReader is a subclass of BufferedReader 
Line number : 5