How to Empty a HashSet in Java
In Java, a HashSet is a collection that contains no duplicate elements. It is implemented as a hash table, which means that the elements are stored in an array based on their hash codes. When you need to remove all elements from a HashSet, there are several methods you can use. This article will guide you through the process of emptying a HashSet in Java.
Method 1: Using the clear() Method
The most straightforward way to empty a HashSet is by using the clear() method. This method removes all of the elements from the set. Here’s an example:
“`java
import java.util.HashSet;
public class Main {
public static void main(String[] args) {
HashSet
hashSet.add(“Apple”);
hashSet.add(“Banana”);
hashSet.add(“Cherry”);
System.out.println(“Before clearing: ” + hashSet);
hashSet.clear();
System.out.println(“After clearing: ” + hashSet);
}
}
“`
In this example, we create a HashSet and add three elements to it. After that, we call the clear() method to remove all elements from the set. The output will show an empty HashSet.
Method 2: Using the Iterator
Another way to empty a HashSet is by using an Iterator. An Iterator is an object that allows you to traverse through the elements of a collection. By using the Iterator, you can remove all elements one by one. Here’s an example:
“`java
import java.util.HashSet;
import java.util.Iterator;
public class Main {
public static void main(String[] args) {
HashSet
hashSet.add(“Apple”);
hashSet.add(“Banana”);
hashSet.add(“Cherry”);
System.out.println(“Before clearing: ” + hashSet);
Iterator
while (iterator.hasNext()) {
iterator.next();
iterator.remove();
}
System.out.println(“After clearing: ” + hashSet);
}
}
“`
In this example, we create a HashSet and add three elements to it. Then, we obtain an Iterator for the HashSet and iterate through its elements. In each iteration, we call the next() method to get the next element and the remove() method to remove it from the set. After the loop, the HashSet will be empty.
Method 3: Using the forEach Loop
Java 8 introduced the forEach loop, which allows you to iterate through a collection and perform an action on each element. You can use the forEach loop to remove all elements from a HashSet. Here’s an example:
“`java
import java.util.HashSet;
public class Main {
public static void main(String[] args) {
HashSet
hashSet.add(“Apple”);
hashSet.add(“Banana”);
hashSet.add(“Cherry”);
System.out.println(“Before clearing: ” + hashSet);
hashSet.forEach(element -> hashSet.remove(element));
System.out.println(“After clearing: ” + hashSet);
}
}
“`
In this example, we create a HashSet and add three elements to it. Then, we use the forEach loop to iterate through the elements and remove them from the set. The output will show an empty HashSet.
In conclusion, there are multiple ways to empty a HashSet in Java. You can use the clear() method, the Iterator, or the forEach loop. Choose the method that best suits your needs and preferences.
