Java TreeSet size() Method

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Description

The Java TreeSet size() method is used to get the number of elements in this set (its cardinality).

Declaration

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

public int size()

Parameters

NA

Return Value

The method call returns the number of elements in this set.

Exception

NA

Getting Size of a TreeSet of Integer Example

The following example shows the usage of Java TreeSet size() method to get the size of the treeset. We've created a TreeSet object of Integer. Then few entries are added using add() method. Using size() method, size of the treeset is printed.

package com.tutorialspoint;

import java.util.TreeSet;

public class TreeSetDemo {
   public static void main(String[] args) {

      // creating a TreeSet 
      TreeSet<Integer> treeset = new TreeSet<Integer>();

      // adding in the tree set
      treeset.add(1);
      treeset.add(13);
      treeset.add(17);
      treeset.add(2);

      // Size of the tree set
      System.out.println("Size of the tree set is: "+treeset.size());      
   }     
}

Output

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

Size of the tree set is: 4

Getting Size of a TreeSet of String Example

The following example shows the usage of Java TreeSet size() method to get the size of the treeset. We've created a TreeSet object of String. Then few entries are added using add() method. Using size() method, size of the treeset is printed.

package com.tutorialspoint;

import java.util.TreeSet;

public class TreeSetDemo {
   public static void main(String[] args) {

      // creating a TreeSet 
      TreeSet<String> treeset = new TreeSet<>();

      // adding in the tree set
      treeset.add("A");
      treeset.add("C");
      treeset.add("B");
      treeset.add("D");

      // Size of the tree set
      System.out.println("Size of the tree set is: "+treeset.size());      
   }     
}

Output

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

Size of the tree set is: 4

Getting Size of a TreeSet of Object Example

The following example shows the usage of Java TreeSet size() method to get the size of the treeset. We've created a TreeSet object of Student objects. Then few entries are added using add() method. Using size() method, size of the treeset is printed.

package com.tutorialspoint;

import java.util.TreeSet;

public class TreeSetDemo {
   public static void main(String[] args) {

      // creating a TreeSet 
      TreeSet<Student> treeset = new TreeSet<>();

      // adding in the tree set
      treeset.add(new Student(2, "Julie"));
      treeset.add(new Student(1, "Robert"));
      treeset.add(new Student(3, "Adam"));
      treeset.add(new Student(4, "Julia"));

      // Size of the tree set
      System.out.println("Size of the tree set is: "+treeset.size());      
   }     
}
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.

Size of the tree set is: 4