Validate a state via its pincode in Java

Question

I need to generate regex to validate state as Tamilnadu based on Pincode validation

Regex which I tried fails at some point

String regex = "^[60-64]{2}{0-9}{4}$";

Ref the Tamil Nadu Pincode info link. It starts with 60-64 as the first two digits, the next 4 digits as 0-9 numbers. It must have six digits.

the code

public boolean isHomeState(String state, String zipcode) {
    if (isValidZipCode(zipcode)) { 
    // ...
    }
    return true;  
}

private boolean isValidZipCode(String zipcode) {
    String regex = "^[60-64]{2}{0-9}{4}$";

    Pattern p = Pattern.compile(regex);
    // If the pin code is empty
    // return false
    if (zipcode == null) {
        return false;
    }

    Matcher m = p.matcher(zipcode);
    return m.matches();
}

A [mcve] with inputs and expected output would help. Without the need to reference an external link that just has a long list, with no explanation. — Robert, Nov 05 '20 at 15:17
Your regex says `[60-64]`. A regular expression is character based, it doesn't know numbers. That means this is treated as a group of 6, 0 to 6, and 4, i.e., 6, 0, 1, 2, 3, 4, 5, 6, 4. You want `6[0-4]` as @Abra wrote. — Robert, Nov 05 '20 at 15:20

score 2 · Answer 1 · answered Nov 05 '20 at 13:44

2

Try the following.

Pattern pattern = Pattern.compile("6[0-4]\\d{4}");

In other words, the digit 6 followed by a digit that is either 0 or 1 or 2 or 3 or 4 and ending with exactly four digits.

answered Nov 05 '20 at 13:44

Abra

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score 0 · Answer 2 · answered Nov 05 '20 at 17:19

There are many regex patterns to do it e.g.

6[0-4][0-9]{4} which means 6 followed by a digit in the range, 0 to 4 which in turn followed by exactly 4 digits.
6[0-4]\d{4} which means 6 followed by a digit in the range, 0 to 4 which in turn followed by exactly 4 digits
6[0-4][0-9][0-9][0-9][0-9] which means 6 followed by a digit in the range, 0 to 4 which in turn followed by exactly 4 digits

However, let's analyze your regex, [60-64]{2}[0-9]{4} which will help you understand the problem better.

The regex, [60-64] means only one of the following:

6
A digit in the range 0 to 6
4

And [60-64]{2} means the above repeated exactly two times i.e. it will match with a combination of 2 digits in the range, 0 to 6 e.g. 00, 60, 34, 01, 10, 11 etc.

As a result, the regex, [60-64]{2}[0-9]{4} will match with first 2 digits consisting of digits in the range, 0 to 6 and next 4 digits consisting of digits in the range, 0 to 9 e.g.

which is not something you expect.

Validate a state via its pincode in Java

2 Answers2

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