ConcurrentMapIn the above example, we first create a `ConcurrentHashMap` and add some key-value pairs. Then, we use the `replace` method to replace the value of an existing key. The first `replace` method replaces the value of the key "two" with 22. The second `replace` method replaces the value of the key "two" with 22 only if its current value is 2. The `replaceAll` method replaces all values in the map with the result of applying the given function to each value. The `java.util.concurrent` package library provides classes and interfaces for creating concurrent, thread-safe applications in Java.map = new ConcurrentHashMap<>(); map.put("one", 1); map.put("two", 2); map.put("three", 3); // Replace the value of an existing key map.replace("two", 22); // Replace the value of an existing key only if its current value is 2 map.replace("two", 2, 22); // Replace all values in the map with the given function map.replaceAll((key, value) -> value * 10);