code: public static void saveBin(DMatrix A, String fileName)
          throws IOException
      {
          FileOutputStream fileStream = new FileOutputStream(fileName);
          ObjectOutputStream stream = new ObjectOutputStream(fileStream);
  
          try {
              stream.writeObject(A);
              stream.flush();
          } finally {
              // clean up
              try {
                  stream.close();
              } finally {
                  fileStream.close();
              }
          }
  
      }
docs: Saves a matrix to disk using Java binary serialization.
  
  @param A The matrix being saved.
  @param fileName Name of the file its being saved at.
  @throws java.io.IOException