ADDITIONAL SYSTEM INFORMATION :
Ubuntu 20.04.1 LTS
openjdk version "11.0.11" 2021-04-20
OpenJDK Runtime Environment 18.9 (build 11.0.11+9)

A DESCRIPTION OF THE PROBLEM :
The problem with RandomAccessFile#length() have been found after using RandomAccessFile#skipBytes() for block device in linux. Method skipBytes always returns 0 skipped bytes for any block device in linux. I made research which showed that method length() was responsible for wrong results of skipBytes() method. I also found that implementation of method length() has changed since Java 9.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
1. Create a random access file stream to read from any device block in linux eg. /dev/sda
2. Run length() method from RandomAccessFile object

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
Correct size of device block returned by length() method from RandomAccessFile object.
ACTUAL -
RandomAccessFile.length() method for block device return always 0

---------- BEGIN SOURCE ----------
import java.io.IOException;
import java.io.RandomAccessFile;

public class Test {
  public static void main(String[] args) throws IOException {
      String blockDevicePath = "/dev/sda";
      RandomAccessFile file = new RandomAccessFile(blockDevicePath,"r");
      System.out.println(blockDevicePath);
      System.out.println("Channel size: "+file.getChannel().size());
      System.out.println("Length: "+file.length());
  }
}
---------- END SOURCE ----------

FREQUENCY : always