Validate IPv4 address in Java

Question

I want to validate an IPv4 address using Java  It should be written using the dot-decimal notation  so it should have 3 dots        no characters  numbers in between the dots  and numbers should be in a valid range  How should it be done

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There are so many ways to achieve that but regular expression is more efficient   Look at the code below   public static void main String   args         String ipStr1    255 245 188 123      valid IP address     String ipStr2    255 245 188 273      invalid IP address - 273 is greater than 255      validateIP ipStr1       validateIP ipStr2      public static void validateIP String ipStr        String regex      b  25 0   5  2 0   4   d  01    d  d         3  25 0   5  2 0   4   d  01    d  d    b       System out println ipStr     is valid      Pattern matches regex  ipStr

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Pretty simple with Regular Expression  but note this is much less efficient and much harder to read than worpet s answer  that uses an Apache Commons Utility   private static final Pattern PATTERN   Pattern compile               01    d  d  2 0-4   d 25 0-5       3   01    d  d  2 0-4   d 25 0-5        public static boolean validate final String ip        return PATTERN matcher ip  matches        Based on post Mkyong

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Write up a suitable regular expression and validate it against that   The JVM have full support for regular expressions

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Try the InetAddressValidator utility class   Docs here   http   commons apache org validator apidocs org apache commons validator routines InetAddressValidator html  Download here   http   commons apache org validator

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Use Guava s  InetAddresses isInetAddress ipStr

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Check if ip is valid        param ip to be checked     return  lt tt gt true lt  tt gt  if  lt tt gt ip lt  tt gt  is valid  otherwise  lt tt gt false lt  tt gt      private static boolean isValid String ip        String   bits   ip split             if  bits length    4            return false            for  String bit   bits            try               if  Integer valueOf bit   lt  0    Integer valueOf bit   gt  255                    return false                          catch  NumberFormatException e                return false     contains other other character                        return true

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If it is IP4  you can use a regular expression as follows     2 0-5  0-5    1  d  d    1-9    d      3  2 0-5  0-5    1  d  d    1-9    d

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If you don care about the range  the following expression will be useful to validate from 1 1 1 1 to 999 999 999 999    1-9  1 3     1-9  1 3     1-9  1 3     1-9  1 3

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Get the valid ip address in two lines using Regular Expression Please check the comment session of code how the regular expression works to get the number range    public class regexTest         public static void main String   args            String IP    255 001 001 255           System out println IP matches new MyRegex   pattern                                d - stands for any number between 0 to 9        d 1 2  - preceding number that 0 to 9 here   can be of 1 digit to 2 digit   so minimum 0 and maximum 99          this stands for or operator                this is applied on a group to get the single value of outcome        0 1  d 2    first digit is either 0 or 1 and other two digits can be any number between   0 to 9        2 0-4  d - first digit is 2   second digit can be between 0 to 4 and last digit can be 0 to 9       25 0-5  - first two digit will be 25 and last digit will be between 0 to 5                    class MyRegex            String zeroTo255       d 1 2   0 1   d 2  2 0-4   d 25 0-5             public String pattern    zeroTo255           zeroTo255           zeroTo255           zeroTo255

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Regular Expression is the most efficient way to solve this problem  Look at the code below  Along validity  it also checks IP address class in which it belongs and whether it is reserved IP Address or not  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  lt  127                                           if arr 0   0  arr 0   127                   return   is Reserved IP Address of Class A                 else if arr 1   0 amp  amp arr 2   0 amp  amp arr 3   0                   return   is Class A Network address                 else if arr 1   255 amp  amp arr 2   255 amp  amp 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  gt  128 amp  amp arr 0  lt  191                         if arr 2   0 amp  amp arr 3   0                   return   is Class B Network address                 else if arr 2   255 amp  amp 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  gt  192 amp  amp arr 0  lt  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  gt  224 amp  amp arr 0  lt  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

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There is also an undocumented utility class sun net util IPAddressUtil  which you should not actually use  although it might be useful in a quick one-off  throw-away utility   boolean isIP   IPAddressUtil isIPv4LiteralAddress ipAddressString     Internally  this is the utility class InetAddress uses to parse IP addresses    Note that this will return true for strings like  123   which  technically are valid IPv4 addresses  just not in dot-decimal notation

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my solution  supports leading 0s      String pattern  quot   0-9    d 1 2  1  0-9  0-9  2  0-4  0-9  25  0-5         d 1 2  1  0-9  0-9  2  0-4  0-9  25 0-5         d 1 2  1  0-9  0-9  2  0-4  0-9  25 0-5         d 1 2  1  0-9  0-9  2  0-4  0-9  25 0-5     quot

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You can use a regex  like this      0-1   0-9  1 2      2 0-4  0-9      25 0-5      3    0-1   0-9  1 2    2 0-4  0-9    25 0-5      This one validates the values are within range   Android has support for regular expressions  See java util regex Pattern   class ValidateIPV4       static private final String IPV4 REGEX       0-1   0-9  1 2       2 0-4  0-9       25 0-5       3    0-1   0-9  1 2    2 0-4  0-9    25 0-5         static private Pattern IPV4 PATTERN   Pattern compile IPV4 REGEX       public static boolean isValidIPV4 final String s                       return IPV4 PATTERN matcher s  matches             To avoid recompiling the pattern over and over  it s best to place the Pattern compile   call so that it is executed only once

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the lib of apache-httpcomponents     ipv4 is true assertTrue InetAddressUtils isIPv4Address  127 0 0 1        not detect the ipv6 assertFalse InetAddressUtils isIPv4Address  2001 0db8 85a3 0000 0000 8a2e 0370 7334       maven lib  update Sep  2019    lt  -- https   mvnrepository com artifact org apache httpcomponents httpclient -- gt   lt dependency gt       lt groupId gt org apache httpcomponents lt  groupId gt       lt artifactId gt httpclient lt  artifactId gt       lt version gt 4 5 10 lt  version gt   lt  dependency gt

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public void setIpAddress String ipAddress            if ipAddress matches         25 0-5  2 0-4  0-9   01   0-9  0-9        3    25 0-5  2 0-4  0-9   01   0-9  0-9            regular expression for ipv4              this ipAddress   ipAddress          else             System out println  incorrect IpAddress

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This is for Android  testing for IPv4 and IPv6 Note  the commonly used InetAddressUtils is deprecated  Use new InetAddress classes public static Boolean isIPv4Address String address        if  address isEmpty              return false            try           Object res   InetAddress getByName address           return res instanceof Inet4Address    res instanceof Inet6Address        catch  final UnknownHostException exception            return false

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The IPAddress Java library will do it   The javadoc is available at the link   Disclaimer  I am the project manager   This library supports IPv4 and IPv6 transparently  so validating either works the same below  and it also supports CIDR subnets as well   Verify if an address is valid      String str    1 2 3 4       IPAddressString addrString   new IPAddressString str       try            IPAddress addr   addrString toAddress                       catch AddressStringException e              e getMessage provides validation issue

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Please see https   stackoverflow com a 5668971 1586965 which uses an apache commons library InetAddressValidator  Or you can use this function -     public static boolean validate final String ip        String PATTERN       0 1  d   d  2 0-4    d  25 0-5    3-9   d       3  0 1  d   d  2 0-4    d  25 0-5    3-9   d           return ip matches PATTERN

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public static boolean isIpv4 String ipAddress        if  ipAddress    null            return false            String ip      1  d 2  2 0-4   d 25 0-5   1-9   d  1-9                       1  d 2  2 0-4   d 25 0-5   1-9   d   d                      1  d 2  2 0-4   d 25 0-5   1-9   d   d                      1  d 2  2 0-4   d 25 0-5   1-9   d   d         Pattern pattern   Pattern compile ip       Matcher matcher   pattern matcher ipAddress       return matcher matches

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Please have a look into IPAddressUtil OOTB class present in sun net util  that should help you

[java] Validate IPv4 address in Java

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