question: public ByteStringBuilder appendUtf8 ( final char [ ] chars ) { if ( chars == null ) { return this ; } final int len = chars . length ; ensureAdditionalCapacity ( len ) ; for ( int i = 0 ; i < len ; i ++ ) { final char c = chars [ i ] ; final byte b = ( byte ) ( c & 0x0000007F ) ; if ( c == b ) { buffer [ this . length + i ] = b ; } else { final Charset utf8 = Charset . forName ( "UTF-8" ) ; final ByteBuffer byteBuffer = utf8 . encode ( CharBuffer . wrap ( chars ) ) ; final int remaining = byteBuffer . remaining ( ) ; ensureAdditionalCapacity ( remaining - len ) ; byteBuffer . get ( buffer , this . length , remaining ) ; this . length += remaining ; return this ; } } this . length += len ; return this ; }
target:  Appends the UTF-8 encoded bytes of the provided char array to this byte string builder.