Регулярное выражение - наиболее эффективный способ решить эту проблему. Посмотрите на код ниже. Вдобавок, он также проверяет класс IP-адреса, в котором он принадлежит, и является ли он зарезервированным IP-адресом или нет
Pattern ipPattern;
int[] arr=new int[4];
int i=0;
//Method to check validity
private String validateIpAddress(String ipAddress) {
Matcher ipMatcher=ipPattern.matcher(ipAddress);
//Condition to check input IP format
if(ipMatcher.matches()) {
//Split input IP Address on basis of .
String[] octate=ipAddress.split("[.]");
for(String x:octate) {
//Convert String number into integer
arr[i]=Integer.parseInt(x);
i++;
}
//Check whether input is Class A IP Address or not
if(arr[0]<=127) {
if(arr[0]==0||arr[0]==127)
return(" is Reserved IP Address of Class A");
else if(arr[1]==0&&arr[2]==0&&arr[3]==0)
return(" is Class A Network address");
else if(arr[1]==255&&arr[2]==255&&arr[3]==255)
return( " is Class A Broadcast address");
else
return(" is valid IP Address of Class A");
}
//Check whether input is Class B IP Address or not
else if(arr[0]>=128&&arr[0]<=191) {
if(arr[2]==0&&arr[3]==0)
return(" is Class B Network address");
else if(arr[2]==255&&arr[3]==255)
return(" is Class B Broadcast address");
else
return(" is valid IP Address of Class B");
}
//Check whether input is Class C IP Address or not
else if(arr[0]>=192&&arr[0]<=223) {
if(arr[3]==0)
return(" is Class C Network address");
else if(arr[3]==255)
return(" is Class C Broadcast address");
else
return( " is valid IP Address of Class C");
}
//Check whether input is Class D IP Address or not
else if(arr[0]>=224&&arr[0]<=239) {
return(" is Class D IP Address Reserved for multicasting");
}
//Execute if input is Class E IP Address
else {
return(" is Class E IP Address Reserved for Research and Development by DOD");
}
}
//Input not matched with IP Address pattern
else
return(" is Invalid IP Address");
}
public static void main(String[] args) {
Scanner scan= new Scanner(System.in);
System.out.println("Enter IP Address: ");
//Input IP Address from user
String ipAddress=scan.nextLine();
scan.close();
IPAddress obj=new IPAddress();
//Regex for IP Address
obj.ipPattern=Pattern.compile("((([0-1]?\\d\\d?|2[0-4]\\d|25[0-5])\\.){3}([0-1]?\\d\\d?|2[0-4]\\d|25[0-5]))");
//Display output
System.out.println(ipAddress+ obj.validateIpAddress(ipAddress));
}