How to validate IP address with regular expression

IP Address Regular Expression Pattern

^([01]?\\d\\d?|2[0-4]\\d|25[0-5])\\.([01]?\\d\\d?|2[0-4]\\d|25[0-5])\\.
([01]?\\d\\d?|2[0-4]\\d|25[0-5])\\.([01]?\\d\\d?|2[0-4]\\d|25[0-5])$

Description:

^ #start of the line
( # start of group #1
[01]?\\d\\d? # Can be one or two digits. If three digits appear, it must start
either 0 or 1
# e.g ([0-9], [0-9][0-9],[0-1][0-9][0-9])
| # …or
2[0-4]\\d # start with 2, follow by 0-4 and end with any digit (2[0-4][0-9])
| # …or
25[0-5] # start with 2, follow by 5 and end with 0-5 (25[0-5])
) # end of group #2
\. # follow by a dot “.”

…. # repeat with 3 time (3x)
$ #end of the line

Whole combination means , digit from 0 to 255 and follow by a dot “.”, repeat 4 time and ending with no dot “.” Valid IP address format is “0-255.0-255.0-255.0-255″.
Java Regular Expression Example


package com.mkyong.regex;

import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class IPAddressValidator{

private Pattern pattern;
private Matcher matcher;

private static final String IPADDRESS_PATTERN =
"^([01]?\\d\\d?|2[0-4]\\d|25[0-5])\\." +
"([01]?\\d\\d?|2[0-4]\\d|25[0-5])\\." +
"([01]?\\d\\d?|2[0-4]\\d|25[0-5])\\." +
"([01]?\\d\\d?|2[0-4]\\d|25[0-5])$";

public IPAddressValidator(){
pattern = Pattern.compile(IPADDRESS_PATTERN);
}

/**
* Validate ip address with regular expression
* @param ip ip address for validation
* @return true valid ip address, false invalid ip address
*/
public boolean validate(final String ip){
matcher = pattern.matcher(ip);
return matcher.matches();
}
}

IP address that match:

1. “1.1.1.1″, “255.255.255.255″,”192.168.1.1″ ,
2. “10.10.1.1″, “132.254.111.10″, “26.10.2.10″,
3. “127.0.0.1″

IP address that doesn’t match:

1. “10.10.10″ – must have 4 “.”
2. “10.10″ – must have 4 “.”
3. “10″ – must have 4 “.”
4. “a.a.a.a” – only digit is allow
5. “10.0.0.a” – only digit is allow
6. “10.10.10.256″ – digit must between [0-255]
7. “222.222.2.999″ – digit must between [0-255]
8. “999.10.10.20″ – digit must between [0-255]
9. “2222.22.22.22″ – digit must between [0-255]
10. “22.2222.22.2″ – digit must between [0-255]
Unit Test – IPAddressValidator


package com.mkyong.regex;

import org.testng.Assert;
import org.testng.annotations.*;

/**
* IPAddress validator Testing
* @author mkyong
*
*/
public class IPAddressValidatorTest {

private IPAddressValidator ipAddressValidator;

@BeforeClass
public void initData(){
ipAddressValidator = new IPAddressValidator();
}

@DataProvider
public Object[][] ValidIPAddressProvider() {
return new Object[][]{
new Object[] {"1.1.1.1"},new Object[] {"255.255.255.255"},
new Object[] {"192.168.1.1"},new Object[] {"10.10.1.1"},
new Object[] {"132.254.111.10"},new Object[] {"26.10.2.10"},
new Object[] {"127.0.0.1"}
};
}

@DataProvider
public Object[][] InvalidIPAddressProvider() {
return new Object[][]{
new Object[] {"10.10.10"},new Object[] {"10.10"},
new Object[] {"10"},new Object[] {"a.a.a.a"},
new Object[] {"10.0.0.a"},new Object[] {"10.10.10.256"},
new Object[] {"222.222.2.999"},new Object[] {"999.10.10.20"},
new Object[] {"2222.22.22.22"},new Object[] {"22.2222.22.2"},
new Object[] {"10.10.10"},new Object[] {"10.10.10"},
};
}

@Test(dataProvider = "ValidIPAddressProvider")
public void ValidIPAddressTest(String ip) {
boolean valid = ipAddressValidator.validate(ip);
System.out.println("IPAddress is valid : " + ip + " , " + valid);
Assert.assertEquals(true, valid);
}

@Test(dataProvider = "InvalidIPAddressProvider",
dependsOnMethods="ValidIPAddressTest")
public void InValidIPAddressTest(String ip) {
boolean valid = ipAddressValidator.validate(ip);
System.out.println("IPAddress is valid : " + ip + " , " + valid);
Assert.assertEquals(false, valid);
}
}

Unit Test – Result

IPAddress is valid : 1.1.1.1 , true
IPAddress is valid : 255.255.255.255 , true
IPAddress is valid : 192.168.1.1 , true
IPAddress is valid : 10.10.1.1 , true
IPAddress is valid : 132.254.111.10 , true
IPAddress is valid : 26.10.2.10 , true
IPAddress is valid : 127.0.0.1 , true
IPAddress is valid : 10.10.10 , false
IPAddress is valid : 10.10 , false
IPAddress is valid : 10 , false
IPAddress is valid : a.a.a.a , false
IPAddress is valid : 10.0.0.a , false
IPAddress is valid : 10.10.10.256 , false
IPAddress is valid : 222.222.2.999 , false
IPAddress is valid : 999.10.10.20 , false
IPAddress is valid : 2222.22.22.22 , false
IPAddress is valid : 22.2222.22.2 , false
PASSED: ValidIPAddressTest([Ljava.lang.String;@1d4c61c)
PASSED: InValidIPAddressTest([Ljava.lang.String;@116471f)

===============================================
com.mkyong.regex.IPAddressValidatorTest
Tests run: 2, Failures: 0, Skips: 0
===============================================

===============================================
mkyong
Total tests run: 2, Failures: 0, Skips: 0
===============================================

Reference

http://en.wikipedia.org/wiki/IP_address

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