Given an IP address, the task is to validate this IP address with the help of Regular Expressions.
The IP address is a string in the form “A.B.C.D”, where the value of A, B, C, and D may range from 0 to 255. Leading zeros are allowed. The length of A, B, C, or D can’t be greater than 3.
Examples:
Input: str = "000.12.12.034" Output: True Input: str = "000.12.234.23.23" Output: False Input: str = "121.234.12.12" Output: True Input: str = "I.Am.not.an.ip" Output: False
Approach:
In this article, the IP address is validated with the help of Regular Expressions or Regex. Below are the steps to solve this problem using ReGex:
- Get the string.
- Regular expression to validate an IP address:
// ReGex to numbers from 0 to 255
zeroTo255 -> (\\d{1, 2}|(0|1)\\d{2}|2[0-4]\\d|25[0-5])
// ReGex to validate complete IP address
IPAddress -> zeroTo255 + "\\." + zeroTo255
+ "\\." + zeroTo255
+ "\\." + zeroTo255;
- where:
- \d represents digits in regular expressions, same as [0-9]
- \\d{1, 2} catches any one or two-digit number
- (0|1)\\d{2} catches any three-digit number starting with 0 or 1.
- 2[0-4]\\d catches numbers between 200 and 249.
- 25[0-5] catches numbers between 250 and 255.
- Match the string with the Regex. In Java, this can be done using Pattern.matcher().
- Return true if the string matches with the given regex, else return false.
Below is the implementation of the above approach:
Java
// Java program to validate an IP address// using Regular Expression or ReGeximport java.util.regex.*;class IPAddressValidation { // Function to validate the IPs address. public static boolean isValidIPAddress(String ip) { // Regex for digit from 0 to 255. String zeroTo255 = "(\\d{1,2}|(0|1)\\" + "d{2}|2[0-4]\\d|25[0-5])"; // Regex for a digit from 0 to 255 and // followed by a dot, repeat 4 times. // this is the regex to validate an IP address. String regex = zeroTo255 + "\\." + zeroTo255 + "\\." + zeroTo255 + "\\." + zeroTo255; // Compile the ReGex Pattern p = Pattern.compile(regex); // If the IP address is empty // return false if (ip == null) { return false; } // Pattern class contains matcher() method // to find matching between given IP address // and regular expression. Matcher m = p.matcher(ip); // Return if the IP address // matched the ReGex return m.matches(); } // Driver code public static void main(String args[]) { // Checking for True case. // Test Case: 1 System.out.println("Test Case 1:"); String str1 = "000.12.12.034"; System.out.println("Input: " + str1); System.out.println( "Output: " + isValidIPAddress(str1)); // Test Case: 2 System.out.println("\nTest Case 2:"); String str2 = "121.234.12.12"; System.out.println("Input: " + str2); System.out.println( "Output: " + isValidIPAddress(str2)); // Checking for False case. // Test Case: 3 System.out.println("\nTest Case 3:"); String str3 = "000.12.234.23.23"; System.out.println("Input: " + str3); System.out.println( "Output: " + isValidIPAddress(str3)); // Test Case: 4 System.out.println("\nTest Case 4:"); String str4 = "I.Am.not.an.ip"; System.out.println("Input: " + str4); System.out.println( "Output: " + isValidIPAddress(str4)); }} |
Output:
Test Case 1: Input: 000.12.12.034 Output: true Test Case 2: Input: 121.234.12.12 Output: true Test Case 3: Input: 000.12.234.23.23 Output: false Test Case 4: Input: I.Am.not.an.ip Output: false
