java - Trying to derive IPv4 address from given IPv4-mapped IPv6 address -

my problem statement says can receive either ipv4 address or v4-mapped v6 address inetsocketaddress instance. if v4-mapped v6 address i've derive v4 address , use that.

i reading javadoc of inetaddresses , says:

 `technically 1 can create 128bit ipv6 address wire format of   "mapped" address, shown above, , transmit in ipv6 packet header.    however, java's inetaddress creation methods appear adhere doggedly    original intent of "mapped" address: "mapped" addresses return    inet4address objects.` 

i can determine if received address v4-mapped v6 address using 1 methods library this:

  // input inetsocketaddress socketaddress    if (inetaddresses.ismappedipv4address(socketaddress.getaddress().gethostaddress())) {         system.out.println("this v4 mapped v6 address");   } 

as per documentation none of libraries (inetsocketaddress, inetaddress or inetaddresses) provides method deriving ipv4 address such mapped input. mean type-casting inetaddress received inetsocketaddress inet4address sufficient?

 inet4address inetaddress = (inet4address) socketaddress.getaddress(); 

if so, need use inetaddresses.ismappedipv4address? how can determine if casting failed or given address neither valid ipv4 address nor v4-mapped v6 address can throw appropriate exception?

the ipaddress java library supports both ipv4 , ipv6 in polymorphic manner. can accomplish describing here.

firstly, using library, inetsocketaddress can ipaddress:

inetsocketaddress inetsocketaddress = ...; ipaddress addr = ipaddress.from(inetsocketaddress.getaddress()); 

from there, can check ipv4 or ipv6:

boolean isipv4 = addr.isipv4(); boolean isipv6 = addr.isipv6(); 

then if ipv6 or ipv6, can use associated subclass. if ipv6, there can check if address ipv4 mapped, ipv4 compatible, , on. if so, can derived ipv4 address. afterwards, can convert java.net type instance.

if(isipv4) {     ipv4address ipv4address = addr.toipv4();     inet4address addr = ipv4address.toinetaddress();     ... } else if(isipv6) {     ipv6address ipv6address = addr.toipv6();     if(ipv6address.isipv4compatible() || ipv6address.isipv4mapped()) {         ipv4address derivedipv4address = ipv6address.getloweripv4address();         inet4address addr = ipv4address.toinetaddress();         ...     } } 

the javadoc available @ link.