When working with zip codes, sometimes we need to validate and match specific patterns. Using regular expressions in Java can be a powerful tool to accomplish this task. In this blog post, we will explore how to use Java regular expressions to match specific zip code patterns.

Java regular expressions overview

Regular expressions in Java are represented by the java.util.regex package. They provide a way to match, search, and manipulate strings based on a specific pattern. To use regular expressions in Java, we typically follow these steps:

1. Create a Pattern object by compiling the regular expression pattern.
2. Create a Matcher object by providing the input string to search for matches.
3. Use methods from the Matcher object to perform specific operations like matching, finding, replacing, etc.

Zip code pattern examples

Let’s consider a few examples of zip code patterns that we might want to match:

1. US zip codes: 5 digits or 5 digits followed by a hyphen and 4 digits (e.g., 12345, 12345-6789).

2. Canadian zip codes: Combination of uppercase letters and digits, separated by a space (e.g., A1A 1A1).

3. UK postal codes: Combination of letters and digits, followed by a space and a digit and two uppercase letters (e.g., EC1A 1BB).

4. Australian zip codes: 4 digits followed by a space and 3 uppercase letters (e.g., 1234 ABC).

Using regular expressions to match zip code patterns

US zip codes

To match US zip codes, we can use the following regular expression pattern:

String usZipCodePattern = "\\d{5}(-\\d{4})?";

Here, \\d{5} represents 5 digits, and (-\\d{4})? allows an optional hyphen followed by 4 digits.

Canadian zip codes

To match Canadian zip codes, we can use the following regular expression pattern:

String canadianZipCodePattern = "[A-Z][0-9][A-Z] [0-9][A-Z][0-9]";

Here, [A-Z][0-9][A-Z] matches an uppercase letter followed by a digit and an uppercase letter, and [0-9][A-Z][0-9] matches a digit followed by an uppercase letter and a digit.

UK postal codes

To match UK postal codes, we can use the following regular expression pattern:

String ukPostalCodePattern = "[A-Z]{1,2}[0-9R][0-9A-Z]? [0-9][A-Z]{2}";

Here, [A-Z]{1,2} matches 1 or 2 uppercase letters, [0-9R][0-9A-Z]? matches a digit or ‘R’ followed by an optional digit or uppercase letter, and [0-9][A-Z]{2} matches a digit followed by 2 uppercase letters.

Australian zip codes

To match Australian zip codes, we can use the following regular expression pattern:

String australianZipCodePattern = "\\d{4} [A-Z]{3}";

Here, \\d{4} matches 4 digits, followed by a space and [A-Z]{3} matches 3 uppercase letters.

Conclusion

Using Java regular expressions, we can easily match specific patterns of zip codes. By understanding the syntax and combining it with the patterns you need, you can validate and manipulate zip codes in your Java applications. Remember to adjust the regular expression patterns based on your specific requirements.

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