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About Ilias Tsagklis

Ilias Tsagklis
Ilias is a software developer turned online entrepreneur. He is co-founder and Executive Editor at Java Code Geeks.

Remove all elements from HashSet example

With this example we are going to demonstrate how to remove all elements from a HashSet. In short, to remove all elements from a HashSet you should:

  • Create a new HashSet.
  • Populate the hashSet with elements, using add(E e) API method of HashSet.
  • Invoke clear() API method of HashSet. The method removes all the elements from the set, so that the set is empty after this call.
  • We can call isEmpty() API method before and after clearing the HashSet, to check if the the set is empty or not.

Let’s take a look at the code snippet that follows:

package com.javacodegeeks.snippets.core;
 
import java.util.HashSet;
 
public class RemoveAllElementsHashSet {
 
  public static void main(String[] args) {
 
    // Create a HashSet and populate it with elements
    HashSet hashSet = new HashSet();
    hashSet.add("element_1");
    hashSet.add("element_2");
    hashSet.add("element_3");
 
    // boolean isEmpty() method checks whether HashSet contains any elements or not   
    System.out.println("HashSet empty : " + hashSet.isEmpty());
 
    // Remove all element from the HashSet using clear() or removeAll() methods
    hashSet.clear();
    System.out.println("HashSet empty : " + hashSet.isEmpty());

  }
}

Output:

HashSet empty : false
HashSet empty : true

 
This was an example of how to remove all elements from a HashSet in Java.

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