question: public static S2CellId fromFaceIJ ( int face , int i , int j ) { long n [ ] = { 0 , face << ( POS_BITS - 33 ) } ; int bits = ( face & SWAP_MASK ) ; for ( int k = 7 ; k >= 0 ; -- k ) { bits = getBits ( n , i , j , k , bits ) ; } S2CellId s = new S2CellId ( ( ( ( n [ 1 ] << 32 ) + n [ 0 ] ) << 1 ) + 1 ) ; return s ; }
target:  Return a leaf cell given its cube face (range 0..5) and i- and j-coordinates (see s2.h).