docs: public synchronized void resizeMatrix(int newsize) throws IOException {
      if(newsize >= 0xFFFF) {
        throw new RuntimeException("Matrix size is too big and will overflow the integer datatype.");
      }
      if(!array.isWritable()) {
        throw new IOException("Can't resize a read-only array.");
      }
      array.resizeFile(arraysize(newsize));
      this.matrixsize = newsize;
      ByteBuffer header = array.getExtraHeader();
      header.putInt(this.matrixsize);
    }