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When dealing with postal codes in global applications, it’s often useful to determine the type of postal code identifier (like ZIP Code, Postcode, etc.) based on a country name. This article shows how to do just that using a clean and scalable Java enum approach.

🧱 Background: PostalCodeType Enum

Let’s say you have an enum that looks like this:

java

public enum PostalCodeType {
    POSTAL_CODE("General"),
    ZIP_CODE("United States"),
    PIN_CODE("India"),
    POSTCODE("United Kingdom, Australia, etc."),
    CEP("Brazil"),
    PLZ_DE("Germany"),
    PLZ_AT("Austria"),
    PLZ_CH("Switzerland"),
    CAP("Italy"),
    EIRCODE("Ireland"),
    NPA("Switzerland"),
    CP("Spain");

    private final String country;

    PostalCodeType(String country) {
        this.country = country;
    }

    public String getCountry() {
        return country;
    }

    @Override
    public String toString() {
        return name() + " (" + country + ")";
    }

    // 🔍 Get enum from country name (partial match)
    public static PostalCodeType fromCountry(String countryName) {
        for (PostalCodeType type : values()) {
            if (type.getCountry().contains(countryName)) {
                return type;
            }
        }
        throw new IllegalArgumentException("No enum constant with country name: " + countryName);
    }
}

🇬🇧 Example: Get Postal Code Type for "United Kingdom"

Here’s how you can retrieve the postal code type associated with the United Kingdom:

java

public class PostalCodeExample {
    public static void main(String[] args) {
        try {
            PostalCodeType ukPostalCodeType = PostalCodeType.fromCountry("United Kingdom");
            System.out.println("Postal Code Type for UK: " + ukPostalCodeType);
        } catch (IllegalArgumentException e) {
            System.out.println(e.getMessage());
        }
    }
}

✅ Output

css

Postal Code Type for UK: POSTCODE (United Kingdom, Australia, etc.)

🛠️ Why Use This Pattern?

• Flexible: Supports partial matches like "United Kingdom" or "Australia".
• Maintainable: Easy to add new types and countries as the enum evolves.
• Safe: Compile-time safety for using specific identifiers, not raw strings.

🚨 Optional: Exact Match Version

Want exact matches only? Just tweak the method:

java

if (type.getCountry().equalsIgnoreCase(countryName)) {
    return type;
}

🧠 Summary

Using a Java enum with a helper method like fromCountry() provides a powerful and maintainable way to map countries to postal code types. Whether you're displaying the appropriate label on forms or validating inputs, this approach scales well across international applications.