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Java - SortedSet Interface

The SortedSet interface extends Set and declares the behavior of a set sorted in an ascending order. In addition to those methods defined by Set, the SortedSet interface declares the methods summarized in the following table −

Several methods throw a NoSuchElementException when no items are contained in the invoking set. A ClassCastException is thrown when an object is incompatible with the elements in a set.

A NullPointerException is thrown if an attempt is made to use a null object and null is not allowed in the set.

SortedSet Interface Methods Sr.No. Method & Description 1

Comparator comparator( )

Returns the invoking sorted set's comparator. If the natural ordering is used for this set, null is returned.

Object first( )

Returns the first element in the invoking sorted set.

SortedSet headSet(Object end)

Returns a SortedSet containing those elements less than end that are contained in the invoking sorted set. Elements in the returned sorted set are also referenced by the invoking sorted set.

Object last( )

Returns the last element in the invoking sorted set.

SortedSet subSet(Object start, Object end)

Returns a SortedSet that includes those elements between start and end.1. Elements in the returned collection are also referenced by the invoking object.

SortedSet tailSet(Object start)

Returns a SortedSet that contains those elements greater than or equal to start that are contained in the sorted set. Elements in the returned set are also referenced by the invoking object.

Operations on SortedSet Interface Creating a SortedSet

TreeSet class implements the SortedSet interface. We can use the TreeSet constructor to create a SortedSet instance. Following is the syntax to create a SortedSet instance:

Syntax

// Create the sorted set
SortedSet<String> set = new TreeSet<>();

Here we're creating a sorted set of String values. This map will store the unique string values. If a duplicate value is added, then that will be discarded.

Adding Value to a SortedSet

SortedSet provides an add() method, which can be used to add value to a SortedSet instance. Whenever a value is added to the set, it is checked against the existing values. If the set is modified then method will return true otherwise false will be returned.

Syntax

public boolean add(E e)

Where E represents the element to be added. If element is already present, then no action will be performed and method will return false.

Example

// Add elements to the set
set.add("b");
set.add("c");
set.add("a");

Getting value from a SortedSet

In order to get values from a SortedSet, we've to get the iterator object from the SortedSet using the iterator() method. Once the iterator object is available then that object can be used to retrieve values present in the SortedSet.

Example

// Iterating over the elements in the set
Iterator it = set.iterator();
while (it.hasNext()) {        
 // Get element
 Object element = it.next();
 System.out.println(element.toString());
}

Deleting a value from a SortedSet

Using the remove(value) method, we can remove the value/object stored in the SortedSet easily.

Syntax

public boolean remove(Object value)

if value is not present in the set, then it will return false otherwise it will remove the value and return true.

set.remove("a");

Iterating SortedSet

SortedSet entries can be easily navigated. SortedSet provides a method iterator() which provides an iterator to navigate all the entries of the set.

Syntax

public Iterator<E> iterator()

Where E is the type of objects to be iterated.

Example

// Iterating over the elements in the set
Iterator it = set.iterator();

while (it.hasNext()) {
 // Get element
 Object element = it.next();
 System.out.println(element.toString());
}

Examples of SortedSet Interface Adding Element to a SortedSet Example

SortedSet have its implementation in various classes like TreeSet. Following is an example of a TreeSet class with add operation−

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

public class SortedSetDemo {

   public static void main(String[] args) {
      // Create the sorted set
      SortedSet<String> set = new TreeSet<>();  

      // Add elements to the set
      set.add("b");
      set.add("c");
      set.add("a");

      // Iterating over the elements in the set
      Iterator it = set.iterator();

      while (it.hasNext()) {
         
         // Get element
         Object element = it.next();
         System.out.println(element.toString());
      }
   }
}

Output

a
b
c

Removing Element from a SortedSet Example

SortedSet have its implementation in various classes like TreeSet. Following is an example of a TreeSet class with add and remove operation −

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

public class SortedSetDemo {

   public static void main(String[] args) {
      // Create the sorted set
      SortedSet<String> set = new TreeSet<>();  

      // Add elements to the set
      set.add("b");
      set.add("c");
      set.add("a");
      set.add("d");
      set.add("e");
      set.add("f");
      
      // remove elements
      set.remove("c");
      set.remove("f");

      // Iterating over the elements in the set
      Iterator it = set.iterator();

      while (it.hasNext()) {
         // Get element
         Object element = it.next();
         System.out.println(element.toString());
      }
   }
}

Output

a
b
d
e

Clearing a SortedSet Example

SortedSet have its implementation in various classes like TreeSet. Following is an example of a TreeSet class with add and clear operation −

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

public class SortedSetDemo {

   public static void main(String[] args) {
      // Create the sorted set
      SortedSet<String> set = new TreeSet<>();  

      // Add elements to the set
      set.add("b");
      set.add("c");
      set.add("a");
      set.add("d");
      set.add("e");
      set.add("f");
      
      System.out.println(set);
      
      // remove elements
      set.clear();
      
      System.out.println(set);
   }
}

Output

[a, b, c, d, e, f]
[]

Advantages of SortedSet Interface

SortedSet ensures that the map is always sorted in ascending order of the values. Whenever a key-value pair is added to the SortedSet, it is re-sorted
Being sorted and unique, SortedSet is very efficient in searches
We can customize the sorting mechanism by using a comparator on the value type.

Disadvantages of SortedSet Interface

As a SortedSet instance has to be sorted every time an entry is added or changed, it becomes a performance bottleneck where changes are very frequent. In such cases, SortedSet is not preferred.
As SortedSet maintains unique records only, we cannot use this collection where duplicate entries can occur in the data set.

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