Design (LLD) Online Voting System  - Machine Coding

Design (LLD) Online Voting System - Machine Coding

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Low-level design (LLD) for an online voting system:

  1. Database design: We will need to store information about voters, candidates, and the votes themselves. This will likely include tables for voters, candidates, and votes, with foreign keys to link them together. We will also need to consider security and privacy concerns, such as ensuring that votes are anonymous and cannot be traced back to individual voters.

  2. User authentication and authorization: Voters will need to be able to log in to the system in order to cast their votes. We will need to implement measures to ensure the security of voter accounts, such as password hashing and potentially two-factor authentication. We will also need to ensure that only eligible voters are able to log in and cast their votes.

  3. Ballot design: The online voting system will need to allow voters to select their preferred candidates or options. This will likely involve creating forms for voters to select their choices, with fields for the candidates or options. We will need to consider usability and accessibility concerns when designing the ballot.

  4. Vote tracking: The system will need to keep track of the votes as they are cast and provide a way for administrators to view the results. This will involve implementing logic to store and count the votes, as well as creating views for the administrators to view the results.

  5. User interface: Finally, we will need to design the user interface for the voting system, including the layout, navigation, and any necessary graphics or styling. This will involve creating wireframes and mockups, as well as implementing the front-end code to bring the design to life.

Here is the complete low-level design (LLD) code for the online voting system in Java:

public class OnlineVotingSystem {
    private VoterDatabase voterDatabase;
    private CandidateDatabase candidateDatabase;
    private Ballot ballot;
    private Encryptor encryptor;
    private AuthenticationService authenticationService;

    public OnlineVotingSystem() {
        voterDatabase = new VoterDatabase();
        candidateDatabase = new CandidateDatabase();
        ballot = new Ballot();
        encryptor = new Encryptor();
        authenticationService = new AuthenticationService();

    public void registerVoter(String name, String password) {
        Voter voter = new Voter(name, password);

    public void addCandidate(String name, String party) {
        Candidate candidate = new Candidate(name, party);

    public void castVote(Voter voter, Candidate candidate) {
        if (authenticationService.authenticate(voter, voterDatabase)) {

    public List<Candidate> getResults() {
        List<Candidate> results = new ArrayList<>();
        for (Candidate candidate : candidateDatabase.getCandidates()) {
            int votes = ballot.getVotes(candidate);
            String encryptedVotes = encryptor.encrypt(votes);
        return results;

public class VoterDatabase {
    private List<Voter> voters;

    public VoterDatabase() {
        voters = new ArrayList<>();

    public void addVoter(Voter voter) {

    public Voter getVoter(String name) {
        for (Voter voter : voters) {
            if (voter.getName().equals(name)) {
                return voter;
        return null;

public class CandidateDatabase {
    private List<Candidate> candidates;

    public CandidateDatabase() {
        candidates = new ArrayList<>();

    public void addCandidate(Candidate candidate) {

    public List<Candidate> getCandidates() {
        return candidates;

public class Ballot {
    private Map<Candidate, Integer> votes;

    public Ballot() {
        votes = new HashMap<>();

    public void addVote(Candidate candidate) {
        if (votes.containsKey(candidate)) {
            votes.put(candidate, votes.get(candidate) + 1);
        } else {
            votes.put(candidate, 1);

    public int getVotes(Candidate candidate) {
        return votes.getOrDefault(candidate, 0);
public class Encryptor {
    public String encrypt(int value) {
        // implement encryption algorithm here
        return "encrypted_" + value;

public class AuthenticationService {
    public boolean authenticate(Voter voter, VoterDatabase voterDatabase) {
        Voter storedVoter = voterDatabase.getVoter(voter.getName());
        if (storedVoter != null && storedVoter.getPassword().equals(voter.getPassword())) {
            return true;
        return false;

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