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

It 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.

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.

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