[Java] Remove Long.bitCount with simple bitmap operations

the `public int isSet(int index)` routine checks if the bit is set by calling Long.bitCount function. This is unnecessary and creates performance degradation. This can simply be replaced by bit shift and bitwise & operation. 

`return Long.bitCount(b & (1L << bitIndex));`

to 

`return (b >> bitIndex) & 0x01;`