use bufferedreader on a txt file twice?

Question

i have to count the lines on a file but later in the code I also have to print what's in that file, but I can't use the reader twice it just says null. How can I work this out without creating a bunch of bufferedreader objects? thanks

just close the stream and create a new object, possible duplicate of http://stackoverflow.com/questions/5421653/reset-buffer-with-bufferedreader-in-java and http://stackoverflow.com/questions/262618/java-bufferedreader-back-to-the-top-of-a-text-file — riteshtch, Mar 06 '16 at 19:53
When you say 'later in the code' do you mean in the same method? You can always have a counter for the number of lines and print the lines. — Rahul Sharma, Mar 06 '16 at 20:00

score 0 · Answer 1 · answered Mar 06 '16 at 19:54

0

Print and count at the same time?
Move the lines to an array then print them?
Make sure you've closed the file before reopening again?

answered Mar 06 '16 at 19:54

Mark Sheekey

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7
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score 0 · Answer 2 · answered Mar 06 '16 at 19:58

Try closing the buffer, and then re-opening it again.

    BufferedReader bufferedReader = new BufferedReader(new FileReader("src/main/java/com/william/sandbox/stackoverflow/samples20160306/Demo.java"));
    String line = bufferedReader.readLine();
    int lineCount = 0;
    while(line != null){
        lineCount += 1;
        line = bufferedReader.readLine();
    }
    System.out.println("Line count is: " + lineCount);

    bufferedReader.close();
    bufferedReader = new BufferedReader(new FileReader("src/main/java/com/william/sandbox/stackoverflow/samples20160306/Demo.java"));

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

score -1 · Answer 3 · answered Mar 06 '16 at 20:07

You can use BufferedReader's mark() and reset() methods to jump back to a specific position.

try (BufferedReader r = new BufferedReader(new FileReader("somefile.txt"))) {
    // marks this position for the next 10 characters read
    // after that the mark is lost
    r.mark(10);

    // do some reading

    // jump back to the mark
    r.reset();
}

Note that, BufferedReader supports marking but not all Readers do. You can use markSupported() to check.

use bufferedreader on a txt file twice?

3 Answers3