这就是问题所在：

while (br.readLine() != null) {
    System.out.println(br.readLine());
}

您有两个对readLine的调用-第一个 only 检查是否有一行（但读取后丢弃），第二个读取 next 行。

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

现在我们只在每个循环迭代中调用readLine()once，并使用我们在“我们完成了吗？”和“打印出该行”部分中读取的行。

你通过while循环读取line，然后通过这个循环读取下一行，所以只需要在while循环中读取它

String s;
 while ((s=br.readLine()) != null) {
     System.out.println(s);
  }

可以将br.readLine()的结果赋给一个变量，并使用它进行处理和检查，如下所示：

String line = br.readLine();
while (line != null) { // You might also want to check for empty?
    System.out.println(line);
    line = br.readLine();
}

对资源使用try。这将自动关闭资源。

try (BufferedReader br = new BufferedReader(new FileReader("C:/test.txt"))) {
    String line;
    while ((line = br.readLine()) != null) {
        System.out.println(line);
    }
} catch (Exception e) {

}

private void readFile() throws Exception {
      AsynchronousFileChannel input=AsynchronousFileChannel.open(Paths.get("E:/dicom_server_storage/abc.txt"),StandardOpenOption.READ);
      ByteBuffer buffer=ByteBuffer.allocate(1024);
      input.read(buffer,0,null,new CompletionHandler<Integer,Void>(){
        @Override public void completed(    Integer result,    Void attachment){
          System.out.println("Done reading the file.");
        }
        @Override public void failed(    Throwable exc,    Void attachment){
          System.err.println("An error occured:" + exc.getMessage());
        }
      }
    );
      System.out.println("This thread keeps on running");
      Thread.sleep(100);
    }

也许你是指这个

public class Reader {

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

    FileReader in = new FileReader("C:/test.txt");
    BufferedReader br = new BufferedReader(in);
    String line = br.readLine();
    while (line!=null) {
        System.out.println(line);
        line = br.readLine();
    }
    in.close();

}

试试看：

String text= br.readLine();
while (text != null) 
{
  System.out.println(text);
  text=br.readLine();
}
in.close();

或

public String getFileStream(final String inputFile) {
        String result = "";
        Scanner s = null;

        try {
            s = new Scanner(new BufferedReader(new FileReader(inputFile)));
            while (s.hasNext()) {
                result = result + s.nextLine();
            }
        } catch (final IOException ex) {
            ex.printStackTrace();
        } finally {
            if (s != null) {
                s.close();
            }
        }
        return result;
}

这也是第一行。

你可以把它存储在数组中，然后使用你想要的任何一行。这是我用来从文件中读取行并将其存储在字符串数组中的代码片段，希望这对你有用：）

public class user {
 public static void main(String x[]) throws IOException{
  BufferedReader b=new BufferedReader(new FileReader("<path to file>"));
  String[] user=new String[30];
  String line="";
  while ((line = b.readLine()) != null) {
   user[i]=line; 
   System.out.println(user[1]);
   i++;  
   }

 }
}