SocialNetwork.java

import java.util.*;

@SuppressWarnings("unused")
public class SocialNetwork {

    public static void main(String[] args) {
        String network = "";

        // Start with an empty network; print it out.
        System.out.println("Initial Network:");
        System.out.println(network);

        // Add three users, swofferh, achen47 and hibbahk, in the correct order and with the friends listed above.
        network = addUser(network, "swofferh", "gbuck21-haleyc22-macy16-mnats-mxw-nwang913-gumball");
        network = addUser(network, "achen47", "ali1726-cartierc-tan7271-yethanli-hzpan8");
        network = addUser(network, "hibbahk", "janvi26-jvdyfu");

        // Print out the network and the network's size.
        System.out.println("Network after adding swofferh, achen47, and hibbahk:");
        System.out.println(network);
        System.out.println("Network size: " + networkSize(network));

        // Remove the user achen47.
        network = removeUser(network, "achen47");

        // Print out the network and the network's size.
        System.out.println("Network after removing achen47:");
        System.out.println(network);
        System.out.println("Network size: " + networkSize(network));

        // Add the user juliak24, with the friends listed above.
        network = addUser(network, "juliak24", "qsun05-ldhar-lukel7-parakhm");

        // Print out the network and the network's size.
        System.out.println("Network after adding juliak24:");
        System.out.println(network);
        System.out.println("Network size: " + networkSize(network));

        // Add the user meravf, with the friends listed above.
        network = addUser(network, "meravf", "rkorol-samkoro-sbabu23-shay2022-sshan854-vwang2");

        // Print out the network and the network's size.
        System.out.println("Network after adding meravf:");
        System.out.println(network);
        System.out.println("Network size: " + networkSize(network));

        // Add the user mxw, with no friends.
        network = addUser(network, "mxw", "");

        // Print out the network and the network's size.
        System.out.println("Network after adding mxw:");
        System.out.println(network);
        System.out.println("Network size: " + networkSize(network));
    }

    // Method to add a user to the network
    public static String addUser(String network, String user, String friends) {
        if (network.isEmpty()) {
            return user + ":" + friends + ",";
        } else {
            return network + user + ":" + friends + ",";
        }
    }

    // Method to count the number of users in the network
    public static int networkSize(String network) {
        if (network.isEmpty()) {
            return 0;
        }
        return network.split(",").length;
    }

    // Method to remove a user from the network
    public static String removeUser(String network, String user) {
        int startIndex = network.indexOf(user + ":");
        if (startIndex == -1) {
            return network; 
        }
        int endIndex = network.indexOf(",", startIndex);
        if (endIndex == -1) {
            return network.substring(0, startIndex);
        }
        String updatedNetwork = network.substring(0, startIndex) + network.substring(endIndex + 1);

        // Remove references to the deleted user from other users' friends lists
        String userToRemove = user + "-";
        String userToRemoveEnd = "-" + user;
        while (updatedNetwork.contains(userToRemove) || updatedNetwork.contains(userToRemoveEnd)) {
            updatedNetwork = updatedNetwork.replace(userToRemove, "").replace(userToRemoveEnd, "");
        }

        return updatedNetwork;
    }
}