1. Overview

Random selection of elements from a Set is a common requirement in various Java applications, especially in games and data processing tasks. In this article, we’ll explore different methods to pick a random element from a Java Set. 2. Using the java.util.Random Class

The java.util.Random class is a handy tool for generating random numbers. To pick a random element from a Set, we can generate a random index and use it to access the element: public static T getByRandomClass(Set set) if (set == null | set.isEmpty()) { throw new IllegalArgumentException(“The Set cannot be empty.”); int randomIndex = new Random().nextInt(set.size()); int i = 0; for (T element : set) { if (i == randomIndex) { return element; } i++; } throw new IllegalStateException(“Something went wrong while picking a random element.”); } Let’s test our method: Set animals = new HashSet<>(); animals.add(“Lion”); animals.add(“Elephant”); animals.add(“Giraffe”); String randomAnimal = getByRandomClass(animals); System.out.println("Randomly picked animal: " + randomAnimal); The result should be random: Randomly picked animal: Giraffe 3. Using the ThreadLocalRandom Class

Starting from Java 7, the ThreadLocalRandom class provides a more efficient and thread-safe alternative for generating random numbers. Here’s how we can use it to pick a random index from a Set: int randomIndex = ThreadLocalRandom.current().nextInt(set.size()); The solution is the same as above except for how the random number is selected. Using ThreadLocalRandom is preferable over java.util.Random because it reduces contention in multi-threaded scenarios and generally offers better performance. 4. Conclusion

In summary, we’ve learned two ways to pick a random element from a Java Set. The example code from this article can be found over on GitHub.