Get readable file size

 
import java.io.File;

public final class Main {
  public static void main(String[] argv){
    System.out.println(getReadableFileSize(10000));
    System.out.println(getReadableFileSize(new File("yourFileName").length()));
  }
  public static String getReadableFileSize(final long fileSize) {
    double l = fileSize * 1D;
    String s = "";
    if (l < 1000) {
      s = fileSize + " B";
    } else {
      l = l / 1024D;
      if (l < 1000) {
        s = l + " KB";
      } else {
        l = l / 1024D;
        if (l < 1000) {
          s = l + " MB";
        } else {
          l = l / 1024D;
          s = l + " GB";
        }
      }
    }
    return (s.length() - s.indexOf('.') <= 3 ? s : s.substring(0, s.indexOf('.') + 3))
        + s.substring(s.indexOf(" "), s.length());
  }

}