TreeSet isEmpty() Method in Java Last Updated : 26 Nov, 2018 Comments Improve Suggest changes Like Article Like Report The Java.util.TreeSet.isEmpty() method is used to check and verify if a TreeSet is empty or not. It returns True if the TreeSet is empty else it returns False. Syntax: Tree_Set.isEmpty() Parameters: The method does not take any parameter Return Value: The function returns True if the set is empty else it returns False. Below program illustrate the use of Java.util.TreeSet.isEmpty() method: Java // Java code to illustrate isEmpty() method import java.util.*; import java.util.TreeSet; public class TreeSetDemo { public static void main(String args[]) { // Creating an empty HashSet TreeSet<String> tree = new TreeSet<String>(); // Use add() method to add elements into the Set tree.add("Welcome"); tree.add("To"); tree.add("Geeks"); tree.add("4"); tree.add("Geeks"); tree.add("TreeSet"); // Displaying the TreeSet System.out.println("TreeSet: " + tree); // Check for the empty set System.out.println("Is the set empty? " + tree.isEmpty()); // Clearing the set using clear() method tree.clear(); // Again Checking for the empty set System.out.println("Is the set empty? " + tree.isEmpty()); } } Output: TreeSet: [4, Geeks, To, TreeSet, Welcome] Is the set empty? false Is the set empty? true Comment More infoAdvertise with us Next Article TreeSet isEmpty() Method in Java chinmoy lenka Follow Improve Article Tags : Misc Java Java-Collections Java - util package Java-Functions java-treeset +2 More Practice Tags : JavaJava-CollectionsMisc Similar Reads TreeSet in Java TreeSet is one of the most important implementations of the SortedSet interface in Java that uses a Tree(red - black tree) for storage. The ordering of the elements is maintained by a set using their natural ordering whether or not an explicit comparator is provided. This must be consistent with equ 13 min read TreeSet add() Method in Java The Java.util.TreeSet.add() method in Java TreeSet is used to add a specific element into a TreeSet. The function adds the element only if the specified element is not already present in the set else the function return False if the element is not present in the TreeSet. Syntax: Tree_Set.add(Object 1 min read TreeSet addAll() Method in Java The java.util.TreeSet.addAll(Collection C) method is used to append all of the elements from the mentioned collection to the existing set. The elements are added randomly without following any specific order. Syntax: boolean addAll(Collection C) Parameters: The parameter C is a collection of any typ 2 min read TreeSet ceiling() method in Java with Examples The ceiling() method of java.util.TreeSet<E> class is used to return the least element in this set greater than or equal to the given element, or null if there is no such element. Syntax: public E ceiling(E e) Parameters: This method takes the value e as a parameter which is to be matched. 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This must be consistent with equals if it is to co 3 min read TreeSet descendingIterator() method in Java with Examples The descendingIterator() method of java.util.TreeSet<E> class is used to return an iterator over the elements in this set in descending order.Syntax: public Iterator descendingIterator()Return Value: This method returns an iterator over the elements in this set in descending order.Below are th 2 min read TreeSet descendingSet() method in Java with Examples The descendingSet() method of java.util.TreeSet<E> class is used to return a reverse order view of the elements contained in this set. The descending set is backed by this set, so changes to the set are reflected in the descending set, and vice-versa. If either set is modified while an iterati 2 min read TreeSet first() Method in Java The Java.util.TreeSet.first() method is used to return the first of the element of a TreeSet. The first element here is being referred to the lowest of the elements in the set. If the elements are of integer types then the smallest integer is returned. If the elements are of the string types then th 3 min read Like