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Showing content from https://www.tutorialspoint.com/java/util/treeset_isempty.htm below:

Java TreeSet isEmpty() Method

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

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

public boolean isEmpty()

NA

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

NA

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());  
   }     
}

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

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());  
   }     
}

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

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;
   }
}

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

java_util_treeset.htm

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