How to convert Java HashSet to List/ArrayList collection

You can convert a HashSet collection to an ArrayList collection by passing the HashSet instance as an argument to the ArrayList constructor call.

Suppose you have the following HashSet instance:

public static void main(String[] args)
{
    HashSet<String> animalSet = new HashSet<>();
    animalSet.add("Tiger");
    animalSet.add("Lion");
    animalSet.add("Hyena");

}

You can convert the animalSet above by initializing an ArrayList and passing the set as an argument to the constructor call as shown below:

public static void main(String[] args)
{
    HashSet<String> animalSet = new HashSet<>();
    animalSet.add("Tiger");
    animalSet.add("Lion");
    animalSet.add("Hyena");

    ArrayList<String> arrList = new ArrayList<>(animalSet);
    System.out.println("arrList content: " + arrList);
    // arrList content: [Lion, Hyena, Tiger]
}

And that’s how you can convert a HashSet to an ArrayList.

If you want to convert the HashSet into a List to avoid using class implementation, you can swap the arrList variable type from ArrayList to List as shown below:

public static void main(String[] args)
{
    HashSet<String> animalSet = new HashSet<>();
    animalSet.add("Tiger");
    animalSet.add("Lion");
    animalSet.add("Hyena");

    List<String> list = new ArrayList<>(animalSet);
    System.out.println("list content: " + list);
    // list content: [Lion, Hyena, Tiger]
}

The result variable will be the same.

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