Java BufferedReader , resetting the reader

Question

I have a particular method where I want to count the number of lines in a text file and then read the file what I am doing is counting the number of lines in the file by iterating over the read.nextLine() and then resetting the buffer and reading from the start of the file again. I am not sure what I am doing wrong

public void ReadFile() throws IOException{
 try{
    FileReader fr = new FileReader(path);
    BufferedReader read = new BufferedReader(fr);
    int numberOfLines=0;
    while(read.readLine()!= null)
    {
        numberOfLines++;  // Getting the number of lines


    }

    read.reset();
    System.out.println(numberOfLines + ": is the no of lines");
    baseString.append(read.readLine());
    baseString.append(read.readLine());
    baseString.append(read.readLine());
    System.out.println(baseString);
 }
 catch(IOException e){
        e.printStackTrace();
 }
}

base string is just a Stringbuffer

private StringBuffer baseString = new StringBuffer();

I explicitly need the count to perform some operation

what is the problem exactly ? and what is baseString ? where it is declared ? — giorashc, Apr 09 '13 at 18:21
Is there a reason why you need to first get the number of lines and then read the file? Can you not count the number of lines while reading it? — Rob Watts, Apr 09 '13 at 18:22
@MarounMaroun it wouldn't be really performing marking the beginning though. — dierre, Apr 09 '13 at 18:54
You should find a way to process the file in one pass. This is just wasteful. — user207421, Apr 09 '13 at 22:28

score 2 · Answer 1 · edited May 23 '17 at 11:43

2

As mentioned here the file is read sequentially by BufferedReader, so you can't go back to the beginning of file with reset of BufferedReader

You have to create new FileReader and BufferedReader

OR

use RandomAccessFile

edited May 23 '17 at 11:43

Community

1
1

answered Apr 09 '13 at 18:24

Anirudha

30,881
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score 1 · Answer 2 · answered Apr 09 '13 at 18:29

1

You need to call mark() on the stream. Reader.reset() isn't guaranteed to work if the stream hasn't been previously marked. The BufferedReader implementation of reset() in particular is only documented as returning to the previous mark.

answered Apr 09 '13 at 18:29

Kenster

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that would not work..take a look at [this](http://stackoverflow.com/questions/262618/java-bufferedreader-back-to-the-top-of-a-text-file) – Anirudha Apr 09 '13 at 18:38

Java BufferedReader , resetting the reader

2 Answers2