Java TreeSet isEmpty() Method

---

---

Description

The Java TreeSet isEmpty() method is used to return true if this set contains no elements.

Declaration

Following is the declaration for java.util.TreeSet.isEmpty() method.

 public boolean isEmpty() 

Parameters

NA

Return Value

The method call returns true if this set contains no elements.

Exception

NA

Checking Empty TreeSet of Integer Example

The following example shows the usage of Java TreeSet isEmpty() method to check if a treeset is empty or not. We've created a TreeSet object of Integer. Then it is checked to be empty using isEmpty() method. Then few entries are added using add() method and map is again checked using isEmpty() method.

 package com.tutorialspoint; import java.util.TreeSet; public class TreeSetDemo { public static void main(String[] args) { // creating a TreeSet TreeSet <Integer>treeset = new TreeSet<>(); // checking tree set System.out.println("Is the tree set empty: "+treeset.isEmpty()); // adding elements in the tree set System.out.println("Adding elements in the tree set"); treeset.add(12); treeset.add(11); treeset.add(16); treeset.add(15); // checking tree set again System.out.println("Is the tree set empty: "+treeset.isEmpty()); } } 

Output

Let us compile and run the above program, this will produce the following result.

 Is the tree set empty: true Adding elements in the tree set Is the tree set empty: false 

Checking Empty TreeSet of String Example

The following example shows the usage of Java TreeSet isEmpty() method to check if a treeset is empty or not. We've created a TreeSet object of String. Then it is checked to be empty using isEmpty() method. Then few entries are added using add() method and map is again checked using isEmpty() method.

 package com.tutorialspoint; import java.util.TreeSet; public class TreeSetDemo { public static void main(String[] args) { // creating a TreeSet TreeSet <String>treeset = new TreeSet<>(); // checking tree set System.out.println("Is the tree set empty: "+treeset.isEmpty()); // adding elements in the tree set System.out.println("Adding elements in the tree set"); treeset.add("A"); treeset.add("B"); treeset.add("C"); treeset.add("D"); // checking tree set again System.out.println("Is the tree set empty: "+treeset.isEmpty()); } } 

Output

Let us compile and run the above program, this will produce the following result.

 Is the tree set empty: true Adding elements in the tree set Is the tree set empty: false 

Checking Empty TreeSet of Object Example

The following example shows the usage of Java TreeSet isEmpty() method to check if a treeset is empty or not. We've created a TreeSet object of Student. Then it is checked to be empty using isEmpty() method. Then few entries are added using add() method and map is again checked using isEmpty() method.

 package com.tutorialspoint; import java.util.TreeSet; public class TreeSetDemo { public static void main(String[] args) { // creating a TreeSet TreeSet <Student>treeset = new TreeSet<>(); // checking tree set System.out.println("Is the tree set empty: "+treeset.isEmpty()); // adding elements in the tree set System.out.println("Adding elements in the tree set"); treeset.add(new Student(1, "Robert")); treeset.add(new Student(2, "Julie")); treeset.add(new Student(3, "Adam")); treeset.add(new Student(4, "Julia")); // checking tree set again System.out.println("Is the tree set empty: "+treeset.isEmpty()); } } class Student implements Comparable<Student> { int rollNo; String name; Student(int rollNo, String name){ this.rollNo = rollNo; this.name = name; } @Override public String toString() { return "[ " + this.rollNo + ", " + this.name + " ]"; } @Override public boolean equals(Object obj) { Student s = (Student)obj; return this.rollNo == s.rollNo && this.name.equalsIgnoreCase(s.name); } @Override public int compareTo(Student student) { return this.rollNo - student.rollNo; } } 

Output

Let us compile and run the above program, this will produce the following result.

 Is the tree set empty: true Adding elements in the tree set Is the tree set empty: false