What is the `putIfAbsent()` method in the `Map` interface?
The `putIfAbsent()` method inserts a key-value pair only if the key does not already exist in the map. If the key is present, it doesn't modify the map.
Correct! The `putIfAbsent()` method is useful when you want to ensure a key is only added if it doesn't already exist.
Can you show an example of how to use `putIfAbsent()` in a `ConcurrentHashMap`?