Deep Copy of a HashSet in Java

HashSet is used to store a unique set of values in Java. It is a class that stores values and provides efficient access. As we know Java uses call-by-reference. So, if we copy a Set and want to make changes to the copied Set, we want it to not affect the element of the original Set. But if it is a shallow copy, then it affects the original set. So, we use a Deep copy of a set, which creates a separate memory for the given set.

If you want to know more about the concept of shallow and deep copy you can go through shallow and deep copy.

Program to perform a deep copy of a HashSet in Java

We can use Copy Constructor in HashSet to achieve Deep copy. Bypassing the original set on the new Set’s constructor. For example, we have a set of Strings and we want to create a deep copy of it.

Below is the implementation of creating Deep Copy Using Copy Constructor:

Java

// Java Program to perform a deep copy of a HashSet
import java.io.*;
import java.util.Arrays;
import java.util.HashSet;

class GFG {
    public static void main(String[] args)
    {
        // Given Set of Strings
        HashSet<String> Set = new HashSet<>(
            Arrays.asList("Geeks", "hello", "gfg"));

        // Deep copy using copy constructor in Hashset.
        HashSet<String> copied_set = new HashSet<>(Set);

        // test the Set
        copied_set.remove("Geeks");

        // show the results
        System.out.println("Original Set " + Set);
        System.out.println("Copied Set" + copied_set);
    }
}

Output

Original Set [Geeks, gfg, hello]
Copied Set[gfg, hello]

Explanation of the above Program:

• This Java program performs a deep copy of a HashSet.
• It starts with a given set of strings.
• Using the copy constructor, it creates a new HashSet named copied_set as a deep copy of the original set.
• The program then removes “Geeks” from the copied set to demonstrate independence.
• Finally, it prints the original and copied sets. In simpler terms, it duplicates a set to create an independent copy, and changes to one set don’t affect the other.