***Java 8 # Unique Country

 

🏗 Step 1: Define the Country Class

public class Country {

    private String countryCode;

    private String countryName;

    private String continent;

 

    // Constructor

    public Country(String countryCode, String countryName, String continent) {

        this.countryCode = countryCode;

        this.countryName = countryName;

        this.continent = continent;

    }

 

    // Getters

    public String getCountryCode() {

        return countryCode;

    }

 

    public String getCountryName() {

        return countryName;

    }

 

    public String getContinent() {

        return continent;

    }

 

    @Override

    public String toString() {

        return countryCode + " - " + countryName + " (" + continent + ")";

    }

}

 

🏗 Step 2: Sort and Collect Using Java 8 Streams

import java.util.*;

import java.util.stream.Collectors;

 

public class CountrySortExample {

    public static void main(String[] args) {

        List<Country> countries = Arrays.asList(

            new Country("IN", "India", "Asia"),

            new Country("US", "United States", "North America"),

            new Country("FR", "France", "Europe"),

            new Country("JP", "Japan", "Asia")

        );

 

        // ✅ Sort by countryName

        List<Country> sortedList = countries.stream()

                .sorted(Comparator.comparing(Country::getCountryName))

                .collect(Collectors.toList());

 

        System.out.println("Sorted Countries:");

        sortedList.forEach(System.out::println);

 

 

        // ✅ Collect unique country names into a Set

        Set<String> countryNames = countries.stream()

                                            .map(Country::getCountryName)

                                            .collect(Collectors.toSet());

 

        System.out.println("\nUnique Country Names:");

        countryNames.forEach(System.out::println);

    }

}

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📊 Output Example

Sorted Countries:

FR - France (Europe)

IN - India (Asia)

JP - Japan (Asia)

US - United States (North America)

 

Unique Country Names:

France

India

Japan

United States

---

🔑 Key Points

• Comparator.comparing(Country::getCountryName) → sorts by countryName.
• .map(Country::getCountryName).collect(Collectors.toSet()) → extracts unique names.
• forEach(System.out::println) → prints results cleanly.

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👉 Do you want me to also show how to sort by multiple fields (e.g., first by continent, then by countryName)? That’s a common real-world requirement when dealing with hierarchical data like countries.