How can I implement Weighted Random Selection in Java?

Weighted Random Selection in Java

When selecting a random item from a set, it's often desirable to bias the selection towards items with higher associated weights. In Java, this can be achieved using a NavigableMap, a specialized data structure specifically tailored for this purpose.

The RandomCollection class, implemented using a NavigableMap, allows weighted items to be added and retrieves random items based on their respective weights. To create a RandomCollection, simply specify a random generator (optional, or use the default Random).

Adding items to the RandomCollection is straightforward. Each item is associated with a weight, which represents its probability of being selected. The total weight is maintained as new items are added.

To select a random item, a random number between 0 and the total weight is generated. The NavigableMap's higherEntry() method is then used to retrieve the first entry with a weight greater than the random number. The value associated with this entry is the randomly selected item.

Example:

RandomCollection<String> rc = new RandomCollection<>();
rc.add(40, "dog").add(35, "cat").add(25, "horse");

for (int i = 0; i < 10; i++) {
    System.out.println(rc.next());
}

This code will generate a random sequence of animals ("dog", "cat", "horse") weighted according to their probabilities.

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