Java SortedSet Interface

The SortedSet interface of the Java collections framework is used to store elements with some order in a set.

It extends the Set interface.

[The Java SortedSet interface extends the Set interface.]

Class that implements SortedSet

In order to use the functionalities of the SortedSet interface, we need to use the TreeSet class that implements it.

[The Java TreeSet class implements the SortedSet interface.]

How to use SortedSet?

To use SortedSet, we must import the java.util.SortedSet package first.

// SortedSet implementation by TreeSet class
SortedSet<String> animals = new TreeSet<>();

We have created a sorted set called animals using the TreeSet class.

Here we have used no arguments to create a sorted set. Hence the set will be sorted naturally.

Methods of SortedSet

The SortedSet interface includes all the methods of the Set interface. It's because Set is a super interface of SortedSet.

Besides methods included in the Set interface, the SortedSet interface also includes these methods:

• comparator() - returns a comparator that can be used to order elements in the set
• first() - returns the first element of the set
• last() - returns the last element of the set
• headSet(element) - returns all the elements of the set before the specified element
• tailSet(element) - returns all the elements of the set after the specified element including the specified element
• subSet(element1, element2) - returns all the elements between the element1 and element2 including element1

Implementation of SortedSet in TreeSet Class

import java.util.SortedSet;
import java.util.TreeSet;

class Main {

    public static void main(String[] args) {
        // Creating SortedSet using the TreeSet
        SortedSet<Integer> numbers = new TreeSet<>();

        // Insert elements to the set
        numbers.add(1);
        numbers.add(2);
        numbers.add(3);
        numbers.add(4);
        System.out.println("SortedSet: " + numbers);

        // Access the element
        int firstNumber = numbers.first();
        System.out.println("First Number: " + firstNumber);

        int lastNumber = numbers.last();
        System.out.println("Last Number: " + lastNumber);

        // Remove elements
        boolean result = numbers.remove(2);
        System.out.println("Is the number 2 removed? " + result);
    }
}

Output

SortedSet: [1, 2, 3, 4]
First Number: 1
Last Number: 4
Is the number 2 removed? true

To learn more about TreeSet, visit Java TreeSet.

Now that we know about the SortedSet interface, we will learn about its implementation using the TreeSet class.