How to get a random line of a text file in Java?

by

Reading the entire file if you want only one line seems a bit excessive. The following should be more efficient:

  1. Use RandomAccessFile to seek to a random byte position in the file.
  2. Seek left and right to the next line terminator. Let L the line between them.
  3. With probability (MIN_LINE_LENGTH / L.length) return L. Otherwise, start over at step 1.

This is a variant of rejection sampling.

Line lengths include the line terminator character(s), hence MIN_LINE_LENGTH >= 1. (All the better if you know a tighter bound on line length).

It is worth noting that the runtime of this algorithm does not depend on file size, only on line length, i.e. it scales much better than reading the entire file.

More Related Contents:

  1. Looping for a random number of times java
  2. How to move elements of Java ArrayList to file in java [closed]
  3. How do I generate random integers within a specific range in Java?
  4. Generating Unique Random Numbers in Java
  5. Downloading a file from spring controllers
  6. Java NIO FileChannel versus FileOutputstream performance / usefulness
  7. Copying files from one directory to another in Java
  8. Reading UTF-8 – BOM marker
  9. Java sending and receiving file (byte[]) over sockets
  10. Math.random() versus Random.nextInt(int)
  11. Difference between java.util.Random and java.security.SecureRandom
  12. byte[] to file in Java
  13. Retrieving a random item from ArrayList [duplicate]
  14. Java: Find .txt files in specified folder
  15. Find place for dedicated application folder
  16. Elegant way to read file into byte[] array in Java [duplicate]
  17. Eclipse reading stdin (System.in) from a file
  18. Writing a file to sdcard
  19. Android : How to read file in bytes?
  20. Java File – Open A File And Write To It [closed]
  21. How to create a new java.io.File in memory? [duplicate]
  22. how to drag and drop files from a directory in java
  23. Trouble with filewriter overwriting files instead of appending to the end
  24. Randomly Generate Letters According to their Frequency of Use?
  25. Choosing random numbers efficiently
  26. How can I get the count of line in a file in an efficient way? [duplicate]
  27. Is there functionality to generate a random character in Java?
  28. Selenium WebDriver: Upload multiple files
  29. Get the file size in android sdk?
  30. Hibernate Criteria API: get n random rows

Leave a Comment