Design Pattern State JAVA

1. State Pattern adalah sebuah design pattern dimana sebuah object bisa mengganti-ganti aksesnya ke object lain untuk menggali informasi, tergantung internal state atau inputnya.
2. Kelebihan State Pattern = Kemudahan untuk menambah class baru yag berasal dari state.
3. Kekurangan State Pattern = Setiap kelas turunan dari state memiliki pengetahuan sambungan yang memperkenalkan dependensi antara subclass.
4. Kapan digunakan State Pattern =
5. Apa yang dilakukan ketika tidak boleh menggunakan State Pattern =

// BankAccountState.java
public interface BankAccountState {
    void inputUsername(String username);
    void inputPassword(String password);
    void wrongUsername();
    void wrongPassword();
}

// Login.java
public class Login {
    BankAccountState hasUsername;
    BankAccountState hasPassword;
    BankAccountState noUsername;
    BankAccountState noPassword;

    BankAccountState accountState;

    int accountAlready = 1;
    boolean correctUsernameEntered = false;
    boolean correctPasswordEntered = false;

    public Login() {
        hasUsername = new HasUsername(this);
        hasPassword = new HasPassword(this);
        noUsername = new NoUsername(this);
        noPassword = new NoPassword(this);

        accountState = noUsername;

        if(accountAlready < 0) {
            accountState = noUsername;
        }
    }

    void setBankAccountState(BankAccountState newBankAccountState) {
        accountState = newBankAccountState;
    }

    public void inputUsername(String Username) {
        accountState.inputUsername(Username);
    }

    public void inputPassword(String Password) {
        accountState.inputPassword(Password);
    }

    public BankAccountState getUsername() {
        return hasUsername;
    }

    public BankAccountState getPassword() {
        return hasPassword;
    }

    public BankAccountState getNoUsername() {
        return noUsername;
    }

    public BankAccountState getNoPassword() {
        return noPassword;
    }
}

// HasUsername.java
public class HasUsername implements BankAccountState {
    Login login;

    public HasUsername(Login newLogin) {
        login = newLogin;
    }

    @Override
    public void inputUsername(String Username) {
        if(Username == "user") {
            System.out.println("Correct Username!");
            login.correctUsernameEntered = true;
            login.setBankAccountState(login.getUsername());
        }

        else {
            System.out.println("Wrong Username!");
            login.correctUsernameEntered = false;
            System.out.println("Please Try Again");
            login.setBankAccountState(login.getNoUsername());
        }
    }

    @Override
    public void inputPassword(String Password) {
        if(Password == "admin") {
            System.out.println("Correct Password!");
            login.correctPasswordEntered = true;
            login.setBankAccountState(login.getPassword());
        }

        else {
            System.out.println("Wrong Password!");
            login.correctPasswordEntered = false;
            System.out.println("Please Try Again");
            login.setBankAccountState(login.getNoPassword());
        }
    }

    @Override
    public void wrongUsername() {
        System.out.println("Wrong Username!");
        login.correctUsernameEntered = false;
        System.out.println("Please Try Again");
        login.setBankAccountState(login.getNoUsername());
    }

    @Override
    public void wrongPassword() {
        System.out.println();
    }
}

// HasPassword.java
public class HasPassword implements BankAccountState {
    Login login;

    public HasPassword(Login newLogin) {
        login = newLogin;
    }

    @Override
    public void inputUsername(String Username) {
        if(Username == "user") {
            System.out.println("Correct Username!");
            login.correctUsernameEntered = true;
            login.setBankAccountState(login.getUsername());
        }

        else {
            System.out.println("Wrong Username!");
            login.correctUsernameEntered = false;
            System.out.println("Please Try Again");
            login.setBankAccountState(login.getNoUsername());
        }
    }

    @Override
    public void inputPassword(String Password) {
        if(Password == "admin") {
            System.out.println("Correct Password!");
            login.correctPasswordEntered = true;
            login.setBankAccountState(login.getPassword());
        }

        else {
            System.out.println("Wrong Password!");
            login.correctPasswordEntered = false;
            System.out.println("Please Try Again");
            login.setBankAccountState(login.getNoPassword());
        }
    }

    @Override
    public void wrongUsername() {
        System.out.println();
    }

    @Override
    public void wrongPassword() {
        System.out.println("Wrong Password!");
        login.correctPasswordEntered = false;
        System.out.println("Please Try Again");
        login.setBankAccountState(login.getNoPassword());
    }
}

// NoUsername.java
public class NoUsername implements BankAccountState {
    Login login;

    public NoUsername(Login newLogin) {
        login = newLogin;
    }

    @Override
    public void inputUsername(String Username) {
        if(Username == "user") {
            System.out.println("Correct Username!");
            login.correctUsernameEntered = true;
            login.setBankAccountState(login.getUsername());
        }

        else {
            System.out.println("Wrong Username!");
            login.correctUsernameEntered = false;
            System.out.println("Please Try Again");
            login.setBankAccountState(login.getNoUsername());
        }
    }

    @Override
    public void inputPassword(String Password) {
        System.out.println("Already Entered Password");
    }

    @Override
    public void wrongUsername() {
        System.out.println("Wrong Username!");
        login.correctUsernameEntered = false;
        System.out.println("Please Try Again");
        login.setBankAccountState(login.getNoUsername());
    }

    @Override
    public void wrongPassword() {
        System.out.println();
    }
}

// NoPassword.java
public class NoPassword implements BankAccountState {
    Login login;

    public NoPassword(Login newLogin) {
        login = newLogin;
    }

    @Override
    public void inputUsername(String Username) {
        System.out.println("Already Entered Username");
    }

    @Override
    public void inputPassword(String Password) {
        if(Password == "admin") {
            System.out.println("Correct Password!");
            login.correctPasswordEntered = true;
            login.setBankAccountState(login.getPassword());
        }

        else {
            System.out.println("Wrong Password!");
            login.correctPasswordEntered = false;
            System.out.println("Please Try Again");
            login.setBankAccountState(login.getNoPassword());
        }
    }

    @Override
    public void wrongUsername() {
        System.out.println();
    }

    @Override
    public void wrongPassword() {
        System.out.println("Wrong Password!");
        login.correctPasswordEntered = false;
        System.out.println("Please Try Again");
        login.setBankAccountState(login.getNoPassword());
    }
}



// TestBankAccount.java
public class TestBankAccount {
    public static void main(String[] args) {
        Login accountState = new Login();
        System.out.println("\t\t\t\tLOGIN");
        System.out.print("Username : ");
        accountState.inputUsername("user");
        System.out.print("Password : ");
        accountState.inputPassword("admin");
    }
}