Java HashSet clone()

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In this guide, you will learn about the HashSet clone() method in Java programming and how to use it with an example.

1. HashSet clone() Method Overview

Definition:

The clone() method of the HashSet class in Java returns a shallow copy of the HashSet instance: the elements themselves are not cloned.

Syntax:

public Object clone()

Parameters:

The method does not take any parameters.

Key Points:

- The clone() method creates a new HashSet instance and inserts all elements of the original set into the new set.

- Changes to the cloned HashSet instance do not affect the original HashSet instance and vice versa.

- The clone() method does not clone the elements themselves; it creates a new set containing references to the same elements.

- The method is not type-safe; it returns an object of type Object, so a type cast is needed to assign it to a HashSet variable.

- The clone() method is generally used to get a backup of the original object in memory.

2. HashSet clone() Method Example

import java.util.HashSet;

public class HashSetCloneExample {

    public static void main(String[] args) {
        HashSet<String> originalSet = new HashSet<>();

        // Adding elements to the original HashSet
        originalSet.add("Apple");
        originalSet.add("Banana");
        originalSet.add("Cherry");

        // Printing the original HashSet
        System.out.println("Original HashSet: " + originalSet);

        // Cloning the original HashSet
        HashSet<String> clonedSet = (HashSet<String>) originalSet.clone();

        // Printing the cloned HashSet
        System.out.println("Cloned HashSet: " + clonedSet);

        // Adding a new element to the cloned HashSet
        clonedSet.add("Date");

        // Printing both HashSets after modification
        System.out.println("Original HashSet after modification: " + originalSet);
        System.out.println("Cloned HashSet after modification: " + clonedSet);
    }
}

Output:

Original HashSet: [Banana, Cherry, Apple]
Cloned HashSet: [Banana, Cherry, Apple]
Original HashSet after modification: [Banana, Cherry, Apple]
Cloned HashSet after modification: [Date, Banana, Cherry, Apple]

Explanation:

In this example, we have an original HashSet containing some elements. 

We then clone this HashSet using the clone() method and make a modification to the cloned set by adding a new element. 

The output demonstrates that the original HashSet remains unaffected by changes to the cloned set, thereby showcasing that a shallow copy of the HashSet has been created.