code: public int[] getIndices(long idx)
  	{
  		int xIndices = (int)idx%dim1;
  		int yIndices = (int)(idx-xIndices)/dim1;
  		int []Indices = {xIndices,yIndices};
  		return Indices;
  	}
docs: long型索引转换为int[]索引
  @param idx
  @return 索引