What Are Sets Data Structure?


Larry Thompson

Sets are a fundamental data structure in computer science, used to store a collection of unique elements. In this article, we will explore what sets are and how they can be utilized in various programming scenarios.

What is a Set?

A set is an unordered collection of distinct elements. Unlike arrays or lists, sets do not allow duplicate values. This means that if you try to add an element that already exists in the set, it will not be added again.

Sets can be used to efficiently perform operations such as checking for the presence of an element, adding and removing elements, and performing set operations like union, intersection, and difference.

Creating a Set

In most programming languages, sets are implemented as built-in data structures. To create a set, you typically need to instantiate the set class or use the set literal syntax.


// Creating an empty set
Set<String> names = new HashSet<>();

// Creating a set with initial values
Set<Integer> numbers = new HashSet<>();

Adding and Removing Elements from a Set

To add an element to a set, you can use the add() method. If the element already exists in the set, it will not be added again.


Set<String> fruits = new HashSet<>();
fruits.add("apple"); // apple already exists in the set

System.out.println(fruits); // Output: [apple, banana, orange]

To remove an element from a set, you can use the remove() method.add(“orange”);


System.println(fruits); // Output: [apple, orange]

Set Operations

Sets provide various operations that can be performed on them. Some of the commonly used set operations include:

  • Union: Combines two sets and returns a new set containing all the unique elements from both sets.
  • Intersection: Returns a new set containing only the common elements between two sets.
  • Difference: Returns a new set containing the elements that exist in one set but not in the other.


Set<String> fruits1 = new HashSet<>();

Set<String> fruits2 = new HashSet<>();

// Union
Set<String> union = new HashSet<>(fruits1);
System.println(union); // Output: [apple, banana, orange, grape]

// Intersection
Set<String> intersection = new HashSet<>(fruits1);
System.println(intersection); // Output: [banana]

// Difference
Set<String> difference = new HashSet<>(fruits1);
System.println(difference); // Output: [apple, orange]


Sets are versatile data structures that allow storing a collection of unique elements. They provide efficient operations for adding, removing, and performing set operations. Understanding sets and their usage can greatly enhance your programming skills.

Now that you have a good understanding of sets, you can start utilizing them in your programs to solve various problems efficiently.

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