Java: Retrieve and remove the first element of a tree set

Last update on May 22 2025 13:15:40 (UTC/GMT +8 hours)

14. Poll First TreeSet Element

Write a Java program to retrieve and remove the first element of a tree set.

Sample Solution:

Java Code:

import java.util.TreeSet;
import java.util.Iterator;

  public class Exercise14 {
  public static void main(String[] args) {
 // creating TreeSet 
   TreeSet <Integer>tree_num = new TreeSet<Integer>();
   TreeSet <Integer>treeheadset = new TreeSet<Integer>();
     
   // Add numbers in the tree
   tree_num.add(10);
   tree_num.add(22);
   tree_num.add(36);
   tree_num.add(25);
   tree_num.add(16);
   tree_num.add(70);
   tree_num.add(82);
   tree_num.add(89);
   tree_num.add(14);
   System.out.println("Original tree set: "+tree_num);
   System.out.println("Removes the first(lowest) element: "+tree_num.pollFirst());
   System.out.println("Tree set after removing first element: "+tree_num);
   }    
}

Sample Output:

Original tree set: [10, 14, 16, 22, 25, 36, 70, 82, 89]                
Removes the first(lowest) element: 10                                  
Tree set after removing first element: [14, 16, 22, 25, 36, 70, 82, 89]

Flowchart:

For more Practice: Solve these Related Problems:

Write a Java program to use pollFirst() on a TreeSet to retrieve and remove the first element, then print the modified set.
Write a Java program to implement a method that recursively removes and returns the first element of a TreeSet.
Write a Java program to compare the first element before and after removal using pollFirst() and then validate the operation.
Write a Java program to use a custom iterator to remove the first element of a TreeSet without using built-in methods.

Go to:

PREV : TreeSet Lower Element.
NEXT : Poll Last TreeSet Element.

Java Code Editor:

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