Sending and receiving messages:

import java.util.*;public class Main { public static void main(String args) { int size = 4; Map<Integer, String> messages = new HashMap<>(); int sender = 0; int receiver = 1; String message = "Hello from process " + sender; messages.put(receiver, message); System.out.println("Process " + sender + " sent message: " + message); if (messages.containsKey(receiver)) { System.out.println("Process " + receiver + " received: " + messages.get(receiver)); } for (int i = 2; i < size; i++) { System.out.println("Process " + i + " is idle (no message)"); } }}