TreeSet in Java | Methods, Example

TreeSet in Java is another major implementation of the Set interface, similar to the HashSet class, with an additional improvement. It sorts items in ascending order, while HashSet does not support any order.

Java TreeSet implements the SortedSet interface. It is a collection that makes it possible to store a set of unique elements (objects) according to their natural order.

It creates a sorted collection that uses a tree structure to store objects or parts. Simply put: In the tree group, the elements are stored and sorted in ascending order.

For example, a series of books can be stored in height or alphabetically by title and author.

In Java TreeSet, elements can be accessed and retrieved relatively quickly thanks to a tree structure. That’s why TreeSet is an excellent choice for quick and easy access to large amounts of sorted data.

The only limitation of using a tree set is that we cannot add double elements to the tree set.

TreeSet class declaration on Java

TreeSet is a generic class declared as a

In this syntax, T defines the type of objects or elements that the set will contain.

TreeSet class hierarchy on Java

The TreeSet class extends AbstractSet and implements the NavigableSet interface. NavigableSet expands SortedSet to provide navigation methods.

TreeSet functions on the Java class

There are some important features of the TreeSet class on Java that you should know. They’re identical:

1. Java TreeSet contains unique elements similar to those of HashSet. Adding a duplicate is not allowed.

2. Access and search times are quite short.
3. With TreeSet it is not possible to insert the zero element.
4. The TreeSet class is not synchronized. That means he’s not sure about the stitches.
5. TreeSet supports ascending order. When we add items to the collection in a random order, the values are automatically displayed and sorted in ascending order.
6. Java TreeSet uses TreeMap internally to store elements.

How do I create a tree set on Java?

TreeSet has the following designers. We can make a copy of TreeSet with the help of one of the four builders.

1. TreeSet() : By default, this constructor creates an empty TreeSet, which is sorted in ascending order in the natural order of the elements.

2. TreeSet(Collection c) : She makes a series of trees and adds them to the collection according to the natural order of their location. All elements added to the new set must implement the similar interface.

If elements of the c-set do not implement the comparable interface or are not compatible with each other, this manufacturer throws the ClassCast exception. If the c-collection contains a null link, this constructor throws the NullPointerException.

3. TreeSet (comp comparator) : This constructor creates an empty tree that is sorted on the comparator specified by comp.

All elements of the entire tree are compared to the specified comparator. A compiler is an interface used to implement the sequence of data.

4. TreeSet(SortedSet s) : This constructor makes an assembly tree with elements of the graded assembly.

Main tree typing methods on Java

The TreeSet class in Java offers different methods to perform different tasks. You’re next:

1. logical addition (object o) : This method is used to add a specific item to this record if it does not already exist.

2. logical completionAll(set c) : This method is used to add all items in the collection.

3. void clear(() : Allows you to delete all items in the set.

4. boolean isEmpty() : This method is used to check whether elements are present in the set. Displays the truth if the file contains no items, otherwise it is false.

5. Boolean distance (object o) : This method is used to remove the specified element from the set if it exists.

6. Boolean contains(object o) : Returns where specified as an element in the set, otherwise false.

7. int Size() : This method is used to obtain the total number of elements in a set.

8. Iterator-Iterator() : The Iterator() method is used to iterate elements in ascending order.

9. Spliterator-Spliterator() : The splititerator() method is used to create a fault-tolerant, late-binding separator on the elements of a tree set.

10. Clone the object() : The clone() method is used to get a flat copy of this copy of TreeSet.

11. Iterator down() : It is used to iterate the elements in descending order.

Important methods defined by the SortedSet interface

Since Java TreeSet implements the SortedSet interface, all methods defined in the SortedSet interface can be used when using the TreeSet class. They’re identical:

1. The object first() : It is used to obtain the first (smallest) element in the graded set.

2. Topic last() : This method returns the last (highest) element of the sorted set.

3. Comparator-Comparison() : It provides a comparator that is used to order the items in a set. If TreeSet uses the natural order, this method returns zero.

4. SortedSet headSet(Object toObject) : This method gives a set of elements that are smaller than the given element.

5. SortedSet subset (item object, item to item) : It returns those elements of the set that fall between the specified range in which the toElement is included and the toElement is excluded.

6. SortedSet tailSet (Object ofElement) : Returns the elements of the set that are greater than or equal to the specified element.

Main methods defined by the NavigableSet interface

Since the Java TreeSet class implements the NavigableSet interface, all methods of this interface can be used when using a TreeSet class. They’re identical:

1. Object ceiling (object o) : Returns the lowest element of the set equal to or greater than the specified element. If such an element is not found, the value zero is returned.

2. Floor of the object (object o) : Returns the most important element of the set, equal to or less than the specified element. If such an element is not found, the element zero is returned.

3. Subject below (Subject o) : This method returns the largest element in the set that is strictly speaking smaller than the given element. If such an element is not found, the zero element is returned.

4. Topic above (topic o) : This method returns the smallest element of the set that is strictly speaking larger than the given element. If such an element is not found, the zero element is returned.

5. The pollFirst() object : It is used to remove and remove the first element from the axle housing.

6. Object pollLast() : It is used to remove and retrieve the last element of the whole tree.

7. NavigableSet descendantSet() : This method returns the elements in reverse order.

8. NavigableSet headSet (object-to-object, including Boolean) : This method returns a set of elements that are less than or equal (if true) to the given element.

9. NavigableSet subset (object deElement, Boolean deInclusive, object àElement, Boolean àInclusive) : This method returns items in the set that fall within the specified range.

10. NavigableSet tailSet (Object ofElement, including Boolean) : It returns elements of the set that are greater than or equal to (if included) the specified element.

Java TreeSet examples for programs

Let’s take different types of sample programs, based on the methods described above and defined by TreeSet, SortedSet and NavigableSet.

Let’s create a program in which we perform various operations, such as adding, checking the size of the set of trees, and the set will be empty or not. For a better understanding, refer to the source code.

Program source code 1 :

import java.util.Set ;
import java.util.TreeSet ;
public class TreeSetEx1 [
public static void main(String[] args)
[
// Create a set of trees
Set ts = new TreeSet<>() ;

// Check whether it is empty or not.
empty boolean = ts.isEmpty();
System.out.println(Is TreeSet empty: +empty) ;

// Check the size of the tree set before adding items to the tree set.
int Size = ts.size();
System.out.println(TreeSet size: +size) ;

// Adding elements to TreeSet.
ts.add(India); // ts.size() – 1.
ts.add(United States); // ts.size() – 2.
ts.add(Australia); // ts.size() – 3.
ts.add(New Zealand); // ts.size() – 4.
ts.add(Switzerland); // ts.size() – 5.

System.out.println(Whole tree sorted: +ts);
int size2 = ts.size();
System.out.println(Size of whole tree after addition of elements: + size2);
}.
}

A way out:
If the TreeSet is empty: Actual size of TreeSet
: 0
Sorting shaft Sorting shaft Sorting shaft Sorting shaft Sorting shaft : Australia, India, New Zealand, Switzerland, United States] Tree size after addition : 5

We create a program in which we perform operations such as deleting an item and checking a particular item.

Program source code 2 :

import java.util.TreeSet ;
public class TreeSetEx2
[
public static empty head(String[] args)
[
TreeSet ts = new TreeSet<>() ;

// Add rows to the entire tree.
ts.add(India);
ts.add(United States);
ts.add(Australia);
ts.add(New Zealand);
ts.add(Switzerland) ;

// Search for a specific item in the kit.
Boolean element = ts.contains(USA) ;
System.out.println(Is USA in the TreeSet : +element) ;

// Remove an element from a tree set.
ts.remove(New Zealand);
System.out.println(Tree sorted: +ts);
ts.clear();
System.out.println(Elements in tree: +ts);
}.
}

A way out:
Is there a United States element in the tree: real
elements: Australia, India, Switzerland, United States] Elements of a tree group : []

We will now create a program that performs various operations based on the methods defined in the SortedSet interface. Look at the source code.

Program source code 3 :

Import from java.util.HashSet;
Import from java.util.Set;
Import from java.util.SortedSet;
Import from java.util.TreeSet;
public class TreeSetEx3
{
public static empty head(String[] args)
{
Set s = new HashSet<>();
s.add(Delhi);
s.add(New York);
s.add(Paris);
s.add(London);
s.add(Delhi); // Adding duplicate elements.

TreeSet ts = new TreeSet<>>>(s);
System.out.println(Set of graded trees: +ts) ;

// Using the methods of the SortedSet interface.
System.out.println(First item: +ts.first());
System.out.println(Last item: +ts.last());
System.out.println(HeadSet elements: +ts.headSet(London));
System.out.println(TailSet elements: +ts.tailSet(London)) ;

SortedSet subSet = ts.subSet (Delhi, Paris);
System.out.println (Subset elements: +subSet);
System.out.println (Sorted Set: +ts.comparator()); // The zero is returned because the natural order is used.
}
}

A way out:
Set of sorted shafts :
First item: DelhiLast article : Paris
Helmet Parts :
TailSet Elements :
elements of the sub-pattern:
Assorted quantity: Zero.

Let’s take the example of a program in which we will perform operations based on the methods of the NavigableSet interface.

Program source code 4 :

import java.util.TreeSet;
public TreeSetEx4
{
public static void main(String[] args)
{
TreeSet ts = new TreeSet<>();
ts.add(25);
ts.add(80);
ts.add(05);
ts.add(100);
ts.add(90);
ts.add(200);
ts.add(300);
System.out.println(set of graded trees: +ts) ;

// Using the methods of the NavigableSet interface.
(Largest element is less than 100: +ts.lower(100));
System.printout (Smallest element is greater than 100: +ts.upper(100));
System.printout (gender: +ts.floor(85));
System.printout (ceiling: +ts.ceiling(10)) ;

System.out.println(ts.pollFirst()); // Remove the first element from the set and remove it.
System.out.println(ts.pollLast()); // Remove the last element from the set and remove it.
System.out.println(New tree record: +ts) ;

System.out.println(HeadSet: +ts.headSet(90, where));
System.out.println(SubSet: +ts.subSet(90, where, 200, where));
}
}

A way out:
Set of sorted shafts : 5, 25, 80, 90, 100, 200, 300] Main element less than 100 : 90
The smallest element is larger than 100 : 200 floors : Ceiling of 80 : 25
5
300
New axes :
Headphones:
Subset: [90, 100, 200]

How can I iterate TreeSet in Java?

In this section we will iterate the TreeSet elements in ascending and descending order using the iterator() method. Take a look at the following source code.

Program source code 5 :

import java.util.Iterator;
import java.util.TreeSet;
open class KeySetDemo
{
open static empty head(string[] args)
{
TreeSet ts = new TreeSet<>();
ts.add(25) ;
ts.add(80) ;
ts.add(05) ;
ts.add(100) ;
ts.add(90) ;

System.out.println(Set of sorted shafts:);
// Bypass elements.
Iterator itr = ts.iterator();
while(itr.hasNext()){
System.out.println(itr.next());
}
System.out.println;
Iterator itr = ts.descendingIterator();
while(it.hasNext()).
{
System.out.println(it.next());
}
}
}

A way out:
Set of sorted shafts :
5
25
80
90
100
Iterative elements per iterator in descending order
100
90
80
25
5

How to sort the TreeSet on Java | Organizing elements in TreeSet.

A set of trees in Java defines the order of the elements in one of two ways:

1. The whole tree sorts the natural order of the elements when implementing the java.lang.Comparable interface. An order with a similar interface is called a natural order. The syntax is given below:

public interface Comparable {
public int comparisonTo(Object o); // Annotation method.

}

The compareTo() method of this interface is implemented by the TreeSet class to compare the current item with the item passed as a command parameter.

If the element argument is smaller than the current element, the method returns +ve integer, zero if they are equal, or -ve integer if the element argument is larger.

2. TreeSet on Java also defines the order of the elements by implementing the comparison interface. Use this method when a TreeSet class needs to apply a different sorting algorithm, regardless of the natural order of the elements.

The comparison interface offers two methods, where the comparison method(() is more important. The syntax is as follows:

public interface Comparator {
public int comparison(element e1, element e2); // Annotation method.
public boolean is equal to (element e); // Abstraction method.

}

The comparison method() of this interface accepts arguments from two objects (elements) and gives an integer value that determines the order in which they are sorted.

This method returns -ve if the first element is smaller than the second, zero if it is equal or +ve if the first element is larger.

When to use TreeSet in Java?

TreeSet can be used when we need unique items in a sorted order.

better used: HashSet or TreeSet?

If you want to store individual items in an orderly order, use TreeSet, otherwise use HashSet without ordering items. That’s because HashSet is much faster than TreeSet.

We hope this tutorial has covered the main points of TreeSet in Java using sample programs. I hope you understand the subject.
Thanks for reading!

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