How to Randomly Select an Element from a Java HashSet or LinkedHashSet?

Random Element Selection from a Set

Choosing a random item from a set is a common operation in various programming scenarios. Java offers different types of sets, including HashSet and LinkedHashSet. Let's examine how to perform this task efficiently.

Choosing a Random Element from HashSet and LinkedHashSet

Java's HashSet and LinkedHashSet provide a convenient way to store unique elements. To pick a random element from these sets, you can follow this approach:

<code class="java">int size = myHashSet.size();
int item = new Random().nextInt(size); // Use a shared Random object in practice
int i = 0;
for (Object obj : myHashSet) {
    if (i == item)
        return obj;
    i++;
}</code>

This technique utilizes the following steps:

1. Determine the size of the set (size).
2. Generate a random integer (item) within the range [0, size-1].
3. Iterate through the set elements, keeping track of the ith element.
4. If i matches the randomly generated index (item), return the current element as the random pick.

This approach ensures uniform distribution in selecting a random element from the set while maintaining the set's order in the case of LinkedHashSet.

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