@Override
	public int compare( Object o1, Object o2 )
	{
		long[] key1 = (long[]) o1;
		long[] key2 = (long[]) o2;
		if( key1[0] < key2[0] )
		{
			return -1;
		}
		if( key1[0] > key2[0] )
		{
			return 1;
		}
		if( key1[0] == key2[0] )
		{
			if( key1[1] == key2[1] )
			{
				return 0;    // equals
			}
			if( key1[1] < key2[1] )
			{
				return -1;
			}
			if( key1[1] > key2[1] )
			{
				return 1;
			}
		}
		return -1;
	}