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SortedSet Interface in Java

Last Updated : 10 Apr, 2026

The SortedSet interface is present in java.util package that extends the Set interface, which maintains unique elements in sorted order, either by natural ordering or a custom comparator.

Elements are maintained in ascending order by default.
Ensures that no duplicate elements are present, consistent with the Set interface.
Null elements are generally not allowed because sorting (natural/comparator) may cause NullPointerException.

Declaration

Since SortedSet is an interface, objects cannot be created directly. Use a class like TreeSet that implements it.

public interface SortedSet<E> extends Set<E>

Java

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

public class GFG{
    
    public static void main(String[] args){
        
        SortedSet<Integer> set = new TreeSet<>();
        set.add(50);
        set.add(20);
        set.add(40);
        set.add(10);

        System.out.println(set);
        System.out.println("First element: " + set.first());
        System.out.println("Last element: " + set.last());
    }
}

Output

[10, 20, 40, 50]
First element: 10
Last element: 50

Explanation:

A TreeSet implements SortedSet.
Elements are automatically sorted in ascending order.
first() and last() return the smallest and largest elements, respectively.

Hierarchy of SortedSet

SortedSet interface extends the Set interface.

Performing Different Operations on SortedSet

1. Adding Elements

To add elements to a SortedSet, use the add() method.In a TreeSet, elements are automatically sorted in ascending order, duplicates are ignored, and null values are not allowed.

Java

import java.util.*;

class Geeks {

    public static void main(String[] args) 
    {
        SortedSet<String> ts = new TreeSet<String>();

        // Elements are added using add() method
        ts.add("A");
        ts.add("B");
        ts.add("C");
        ts.add("A");

        System.out.println(ts);
    }
}

Output

[A, B, C]

2. Accessing the Elements

We can access elements using methods such as contains(), first(), last(), etc.

Java

import java.util.*;
class Geeks {

    public static void main(String[] args)
    {
        SortedSet<String> ts = new TreeSet<String>();

        // Elements are added using add() method
        ts.add("A");
        ts.add("B");
        ts.add("C");
        ts.add("A");

        System.out.println("Sorted Set is: " + ts);

        String check = "D";

        // Check if the above string exists in the SortedSet or not
        System.out.println("Contains: " + check + " " 
                           + ts.contains(check));

        // Print the first element in the SortedSet
        System.out.println("First Value: " + ts.first());

        // Print the last element in the SortedSet
        System.out.println("Last Value: " + ts.last());
    }
}

Output

Sorted Set is: [A, B, C]
Contains: D false
First Value: A
Last Value: C

3. Removing the Values

The values can be removed from the SortedSet using the remove() method.

Java

import java.util.*;
class Geeks {

    public static void main(String[] args)
    {
        SortedSet<String> ts = new TreeSet<>();

        // Elements are added using add() method
        ts.add("A");
        ts.add("B");
        ts.add("C");
        ts.add("B");
        ts.add("D");
        ts.add("E");

        System.out.println("Initial TreeSet: " + ts);

        // Removing the element b
        ts.remove("B");

        System.out.println("After removing element: " + ts);
    }
}

Output

Initial TreeSet: [A, B, C, D, E]
After removing element: [A, C, D, E]

4. Iterating through the SortedSet

There are various ways to iterate through the SortedSet. The most famous one is to use the enhanced for loop.

Java

import java.util.*;
class Geeks
 { 
    public static void main(String[] args)
    {
        SortedSet<String> ts
            = new TreeSet<String>();
 
        // Elements are added using add() method
        ts.add("C");
        ts.add("D");
        ts.add("E");
        ts.add("A");
        ts.add("B");
        ts.add("Z");
 
        // Iterating though the SortedSet
        for (String value : ts)
            System.out.print(value
                             + ", ");
        System.out.println();
    }
}

Output

A, B, C, D, E, Z,

Note: The class which implements the SortedSet interface is TreeSet.

Methods of SortedSet Interface

The following are the methods present in the SortedSet interface. Here, the “*” represents that the methods are part of the Set interface.

Method	Description
add(element)	Adds an element if not already present.
addAll(collection)	Adds all elements from another collection.
clear()	Removes all elements (set remains empty).
comparator()	This method returns the comparator used to order the elements in this set.
contains(element)	This method is used to check whether a specific element is present in the Set or not.
containsAll(collection)	Checks if all elements of a collection are in the set.
first()	This method returns the first(lowest) element present in this set.
hashCode()	Returns the hash code of the set.
headSet(element)	This method returns the elements which are less than the element that are present in the sorted set.
isEmpty()	This method is used to check if a SortedSet is empty or not.
last()	This method returns the last(highest) element present in the set.
remove(element)	Removes the given element
removeAll(collection)	Removes all matching elements from the set.
retainAll(collection)	Keeps only elements present in the given collection.
size()	Returns the number of elements in the set.
subSet(element1, element2)	This method returns a sorted subset from the set containing the elements between element1 and element2.
tailSet(element)	This method returns the elements which are greater than or equal to the element that are present in the sorted set.
toArray()	This method is used to form an array of the same elements as that of the Set.

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