# How to check Aadhar number is valid or not using Regular Expression

Given a string str, the task is to check whether the given string is a valid Aadhar number or not by using Regular Expression. The valid Aadhar number must satisfy the following conditions:

1. It should have 12 digits.
2. It should not starts with 0 and 1.
3. It should not contains any alphabet and special characters.
4. It should have white space after every 4 digits.

Examples:

Input: str = “3675 9834 6012”
Output: true
Explanation:
The given string satisfies all the above mentioned conditions. Therefore it is a valid Aadhar number.

Input: str = “3675 9834 6012 8”
Output: false
Explanation:
The given string contains 13 digits. Therefore it is not a valid Aadhar number.

## Recommended: Please try your approach on {IDE} first, before moving on to the solution.

Approach: The idea is to use the Regular Expression to solve this problem. The following steps can be followed to compute the answer:

1. Get the String.
2. Create a regular expression to check valid Aadhar number as mentioned below:

regex = “^[2-9]{1}[0-9]{3}\\s[0-9]{4}\\s[0-9]{4}\$”;

Where:

• ^ represents the starting of the string.
• [2-9]{1} represents the first digit should be any from 2-9.
• [0-9]{3} represents the next 3 digits after first digit should be any digit from 0-9.
• \\s represents the white space.
• [0-9]{4} represents the next 4 digits should be any from 0-9.
• \\s represents the white space.
• [0-9]{4} represents the next 4 digits should be any from 0-9.
• \$ represents the ending of the string.
3. Match the given string with the regular expression. In Java, this can be done by using Pattern.matcher().
4. Return true if the string matches with the given regular expression, else return false.

Below is the implementation of the above approach:

 `// Java program to check valid ` `// Aadhar number using regex. ` ` `  `import` `java.util.regex.*; ` `class` `GFG { ` ` `  `    ``// Function to validate Aadhar number. ` `    ``public` `static` `boolean` `    ``isValidAadharNumber(String str) ` `    ``{ ` `        ``// Regex to check valid Aadhar number. ` `        ``String regex ` `            ``= ``"^[2-9]{1}[0-9]{3}\\s[0-9]{4}\\s[0-9]{4}\$"``; ` ` `  `        ``// Compile the ReGex ` `        ``Pattern p = Pattern.compile(regex); ` ` `  `        ``// If the string is empty ` `        ``// return false ` `        ``if` `(str == ``null``) { ` `            ``return` `false``; ` `        ``} ` ` `  `        ``// Pattern class contains matcher() method ` `        ``// to find matching between given string ` `        ``// and regular expression. ` `        ``Matcher m = p.matcher(str); ` ` `  `        ``// Return if the string ` `        ``// matched the ReGex ` `        ``return` `m.matches(); ` `    ``} ` ` `  `    ``// Driver Code. ` `    ``public` `static` `void` `main(String args[]) ` `    ``{ ` ` `  `        ``// Test Case 1: ` `        ``String str1 = ``"3675 9834 6015"``; ` `        ``System.out.println(isValidAadharNumber(str1)); ` ` `  `        ``// Test Case 2: ` `        ``String str2 = ``"4675 9834 6012 8"``; ` `        ``System.out.println(isValidAadharNumber(str2)); ` ` `  `        ``// Test Case 3: ` `        ``String str3 = ``"0175 9834 6012"``; ` `        ``System.out.println(isValidAadharNumber(str3)); ` ` `  `        ``// Test Case 4: ` `        ``String str4 = ``"3675 98AF 60#2"``; ` `        ``System.out.println(isValidAadharNumber(str4)); ` ` `  `        ``// Test Case 5: ` `        ``String str5 = ``"417598346012"``; ` `        ``System.out.println(isValidAadharNumber(str5)); ` `    ``} ` `} `

Output:

```true
false
false
false
false
```

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