Java TreeSet clear() Method

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Description

The Java TreeSet clear() method is used to remove all of the elements from this set.

Declaration

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

public void clear()

Parameters

NA

Return Value

NA

Exception

NA

Clearing a TreeSet of Integer Example

The following example shows the usage of Java TreeSet clear() method to add entries to the treeset. We've created a TreeSet object of Integer. Then few entries are added using add() method and treeset object is printed to check its content then we've cleared the treeset and printed its size again to validate the contents.

package com.tutorialspoint;

import java.util.TreeSet;

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

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

      // adding in the tree set
      treeset.add(12);
      treeset.add(13);
      treeset.add(14);
      treeset.add(15);
      
      // displaying the Tree set data
      System.out.println("Tree set : " + treeset);
      
      // clearing the set
      System.out.println("Clearing tree"); 
      treeset.clear();
      System.out.println("Size of the tree: "+treeset.size());      
   }     
}

Output

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

Tree set : [12, 13, 14, 15]
Clearing tree
Size of the tree: 0

Clearing a TreeSet of String Example

The following example shows the usage of Java TreeSet clear() method to add entries to the treeset. We've created a TreeSet object of String. Then few entries are added using add() method and treeset object is printed to check its content then we've cleared the treeset and printed its size again to validate the contents.

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("12");
      treeset.add("13");
      treeset.add("14");
      treeset.add("15");
      
      // displaying the Tree set data
      System.out.println("Tree set : " + treeset);
      
      // clearing the set
      System.out.println("Clearing tree"); 
      treeset.clear();
      System.out.println("Size of the tree: "+treeset.size());      
   }     
}

Output

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

Tree set : [12, 13, 14, 15]
Clearing tree
Size of the tree: 0

Clearing a TreeSet of Object Example

The following example shows the usage of Java TreeSet clear() method to add entries to the treeset. We've created a TreeSet object of Student objects. Then few entries are added using add() method and treeset object is printed to check its content then we've cleared the treeset and printed its size again to validate the contents.

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(1, "Robert"));
      treeset.add(new Student(2, "Julie"));
      treeset.add(new Student(3, "Adam"));
      treeset.add(new Student(4, "Julia"));
      
      // displaying the Tree set data
      System.out.println("Tree set : " + treeset);
      
      // clearing the set
      System.out.println("Clearing tree"); 
      treeset.clear();
      System.out.println("Size of the tree: "+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.

Tree set : [[ 1, Robert ], [ 2, Julie ], [ 3, Adam ], [ 4, Julia ]]
Clearing tree
Size of the tree: 0