code: public static boolean destroy(File file) {
          if (!file.exists()) return false;
  
          RandomAccessFile f = null;
          long size = file.length();
          try {
              f = new RandomAccessFile(file, "rw");
              long rec = size/DMSG.length();
              int left = (int)(size - rec*DMSG.length());
              while(rec != 0) {
                  f.write(DMSG.getBytes(), 0, DMSG.length());
                  rec--;
              }
              if (left > 0) {
                  f.write(DMSG.getBytes(), 0, left);
              }
          } catch(Exception e) {
              return false;
          } finally {
              try {
                  if (f != null) f.close();
              } catch(Exception e) {}
          }
  
          return file.delete();
      }
docs: Overwrites the contents of the file with a random
  string and then deletes the file.
  
  @param file file to remove