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 ends with 0-5 (25[0-5])
)		#  end of group #2
\.            #  follow by a dot "."
....            # repeat with 3 times (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”.

## 1. Java Regular Expression Example

``````
package com.mkyong.regex;

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

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])\$";

}

/**
* 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();
}
}
``````

## 2. IP address that matches :

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”

## 3. IP address that doesnâ€™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 has allowed
5. “10.0.0.a” – only digit has allowed
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]

## 4. Unit Test

``````
package com.mkyong.regex;

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

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

@BeforeClass
public void initData(){
}

@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"},
};
}

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

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

## 5. 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