public static int previousClearBit ( long v , int start ) { if ( start < 0 ) { return - 1 ; } start = start < Long . SIZE ? start : Long . SIZE - 1 ; long cur = ~ v & ( LONG_ALL_BITS >>> - ( start + 1 ) ) ; return cur == 0 ? - 1 : 63 - Long . numberOfLeadingZeros ( cur ) ; }
Find the previous clear bit .