HashSet – In Java

import java.util.HashSet;

public class Program3 {

    public static void main(String[] args) {

        HashSet<String> country = new HashSet<String>();
        country.add("India");
        country.add("USA");
        country.add("China");
        country.add("Russia");

        System.out.println(country);

    }
}

Output –

[USA, China, India, Russia]

Note: The order may change every time you run the program. That’s because HashSet does not maintain insertion order.

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🔍 What is a HashSet?

• HashSet is a collection of unique elements — duplicates are not allowed.

• It is part of Java’s Collection Framework.

• It is unordered — the elements may not appear in the order you added them.

💡 Key Features:

Feature	Description
No Duplicates	Automatically ignores duplicate entries
Fast Lookup	Uses hashing for quick access
No Order Guarantee	Elements can appear in any order

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❗ Example: Adding Duplicate

country.add(“India”); // Duplicate
System.out.println(country); // “India” will not be added again


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🔁 Looping Through a HashSet:

for (String c : country) {


System.out.println("Country: " + c);


}


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📦 When to Use HashSet:

• When you need to store unique values.

• When you don’t care about the order.

• Useful for things like tags, sets of IDs, or filtering duplicates.