question: public static byte [ ] flipAllBitsInPlace ( byte [ ] bytes , int index , int length ) { int endIndex = Math . min ( bytes . length , index + length ) ; for ( int i = index ; i < endIndex ; i ++ ) { bytes [ i ] = ( byte ) ( bytes [ i ] ^ 0xff ) ; } return bytes ; }
target:  This flips the bits in the range [index, index + length) and returns the same byte[].