question: public static boolean isValidIPv4 ( String address ) { if ( address . length ( ) == 0 ) { return false ; } int octet ; int octets = 0 ; String temp = address + "." ; int pos ; int start = 0 ; while ( start < temp . length ( ) && ( pos = temp . indexOf ( '.' , start ) ) > start ) { if ( octets == 4 ) { return false ; } try { octet = Integer . parseInt ( temp . substring ( start , pos ) ) ; } catch ( NumberFormatException ex ) { return false ; } if ( octet < 0 || octet > 255 ) { return false ; } start = pos + 1 ; octets ++ ; } return octets == 4 ; }
target:  Validate the given IPv4 address.