In computer science, a Set is a data structure that stores a collection of unique elements. It is typically implemented using a hash table or a binary search tree, and provides efficient operations for adding, removing, and checking for the presence of elements. Sets are commonly used in algorithms and data processing tasks where duplicate elements are not allowed or need to be removed. They are also used in database systems to enforce uniqueness constraints on data. Keep reading below to learn how to use a Set in Java.

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How to use a Set in Java with example code

A Set is a collection in Java that does not allow duplicate elements. It is an interface that extends the Collection interface. The Set interface is implemented by several classes in Java, including HashSet, TreeSet, and LinkedHashSet.

To use a Set in Java, you first need to import the java.util.Set package. Then, you can create a Set object using one of the implementing classes. For example, to create a HashSet object, you can use the following code:

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

This creates a Set object that can hold String elements. You can replace “String” with any other data type you want to use.

To add elements to the Set, you can use the add() method. For example:


This adds the String “apple” to the Set. If you try to add “apple” again, it will not be added because Sets do not allow duplicates.

To remove an element from the Set, you can use the remove() method. For example:


This removes the String “apple” from the Set.

You can also check if a Set contains a specific element using the contains() method. For example:

if (set.contains("apple")) {
System.out.println("Set contains apple");

This checks if the Set contains the String “apple” and prints a message if it does.

Finally, you can iterate over the elements in a Set using a for-each loop. For example:

for (String element : set) {

This prints each element in the Set on a new line.

In summary, Sets are a useful collection in Java that do not allow duplicates. They can be created using one of the implementing classes, and elements can be added, removed, and checked for using various methods. Iterating over the elements in a Set is also easy using a for-each loop.

What is a Set in Java?

In conclusion, a Set in Java is a collection that stores unique elements. It is an essential data structure that helps in solving many programming problems efficiently. The Set interface provides several methods to add, remove, and check the presence of elements in the collection. The HashSet and TreeSet classes are the most commonly used implementations of the Set interface in Java. HashSet provides constant-time performance for basic operations, while TreeSet maintains elements in a sorted order. Understanding the concept of Sets in Java is crucial for any Java developer, as it can help in writing efficient and optimized code.

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