Files

[lakshmibvaraprasad]

Hi,

I have a input file with records. I have line numbers randomly and I have stored these line numbers in an array. . I need to retrieve the records from input file using the line numbers which are in array.

[JosAH]

Hi,

I have a input file with records. I have line numbers randomly and I have stored these line numbers in an array. . I need to retrieve the records from input file using the line numbers which are in array.

If those records have a fixed length (they're all equal) you can use a RandomAccessFile, otherwise you have to read each and every record and check the line number counter.

kind regards,

Jos

[Norm]

I need to retrieve the records from input file using the line numbers which are in array.

Is it a sequential file with variable length records or are the records all the same length?
For the normal, sequential text file, you will have to read the records in order starting at the first one.
If the records are fixed length you can use the RandomAccessFile class to read them as required vs sequentially.

[lakshmibvaraprasad]

Thanks for your reply. My input file records are of same length and separated by tabs. I have random line number in an array. Now I need to retrieve records from the input file using random line number. Can you give an example or logic that would help me a lot?

[Norm]

There are code samples here. Use Search or Google for samples of RandomAccessClass.

My input file records are of same length and separated by tabs

The tabs are irrelevant. The contents of any record is irrelevant. Each record must have exactly the same number of characters.
Say the records are 10 characters long, the first record is at location 0, 2nd at 10, third at 20, 4th at 30 etc

[lakshmibvaraprasad]

Hello,

I am sorry. Their was a mistake in my question. Here is the exact question what I mean. I need to retrieve the lines(these are separated by tabs) from the input file using the line numbers(these are in random) which are stored in array.

[Norm]

I need to retrieve the lines(these are separated by tabs)

Then you will need to read the file starting at byte 0 and count the lines as you go.

[lakshmibvaraprasad]

This helped me. In files, we have readLine() class to read next line of the file pointer. Like this,Is their any class to read before line of the file pointer?

[Norm]

What class are you talking about? I don't know what the file pointer is.