Hierarchical software design example

public class CustomersTask {

    private CustomersTaskContext customersTaskContext;
    private PrintCustomersContext printCustomersContext;
    private ReadCustomers readCustomers;
    private PrintCustomers printCustomers;

    public CustomersTask(CustomersTaskContext customersTaskContext) {
        this.customersTaskContext = customersTaskContext;
        customersTaskInit();
    }

    public final void customersTaskInit() {
        printCustomersContext 
                = new PrintCustomersContext(getCustomersTaskContext());
        readCustomers = new ReadCustomers(getCustomersTaskContext());
        printCustomers = new PrintCustomers(getPrintCustomersContext());
    }

    public final void printCustomersTask() throws IOException {
        readCustomers();
        printCustomers();
    }

    public static void main(String args[]) {
        try {
            String filename = args[0];
            CustomersTaskContext ctc = new CustomersTaskContext();
            ctc.init(filename);
            CustomersTask ct = new CustomersTask(ctc);
            ct.printCustomersTask();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    private CustomersTaskContext getCustomersTaskContext() {
        return customersTaskContext;
    }

    private PrintCustomersContext getPrintCustomersContext() {
        return printCustomersContext;
    }

    private PrintCustomers getPrintCustomers() {
        return printCustomers;
    }

    private void printCustomers() {
        getPrintCustomers().printCustomers();
    }

    private ReadCustomers getReadCustomers() {
        return readCustomers;
    }

    private void readCustomers() throws IOException {
        getReadCustomers().readCustomers();
    }
}

public class PrintCustomers {

    private PrintCustomersContext printCustomersContext;
    private PrintCustomer printCustomer;

    public PrintCustomers(PrintCustomersContext printCustomersContext) {
        this.printCustomersContext = printCustomersContext;
        printCustomersInit();
    }

    public final void printCustomersInit() {
        printCustomer = new PrintCustomer(getPrintCustomersContext());
    }

    public final void printCustomers() {
        for (Customer customer : getCustomerList()) {
            printCustomer(customer);
        }
    }

    private PrintCustomersContext getPrintCustomersContext() {
        return printCustomersContext;
    }

    private PrintCustomer getPrintCustomer() {
        return printCustomer;
    }

    private CustomersTaskContext getCustomersTaskContext() {
        return getPrintCustomersContext().getCustomersTaskContext();
    }

    private void printCustomer(Customer customer) {
        getPrintCustomer().printCustomer(customer);
    }

    private CustomerData getCustomerData() {
        return getCustomersTaskContext().getCustomerData();
    }

    private LinkedList getCustomerList() {
        return getCustomerData().getCustomerList();
    }
}

© Ravindra Mahajan

public class CustomersTaskContext {

    private String filename;
    private CustomerData customerData;

    public CustomersTaskContext() {
    }

    public void init(String filename) {
        this.filename = filename;
        this.customerData = new CustomerData();
    }

    public final String getFilename() {
        return filename;
    }

    public final CustomerData getCustomerData() {
        return customerData;
    }
}

public class ReadCustomers {

    private CustomersTaskContext customersTaskContext;

    public ReadCustomers(CustomersTaskContext customersTaskContext) {
        this.customersTaskContext = customersTaskContext;
    }

    public final void readCustomers() throws IOException {
        FileReader fr = new FileReader(getFilename());
        BufferedReader br = new BufferedReader(fr);
        String name = br.readLine();
        while (name != null) {
            Customer customer = new Customer(name);
            addCustomer(customer);
            name = br.readLine();
        }
        br.close();
    }

    private CustomersTaskContext getCustomersTaskContext() {
        return customersTaskContext;
    }

    private String getFilename() {
        return getCustomersTaskContext().getFilename();
    }

    private CustomerData getCustomerData() {
        return getCustomersTaskContext().getCustomerData();
    }

    private boolean addCustomer(Customer customer) {
        return getCustomerData().addCustomer(customer);
    }
}

public class PrintCustomersContext {

    private CustomersTaskContext customersTaskContext;

    public PrintCustomersContext(CustomersTaskContext ctc) {
        this.customersTaskContext = ctc;
    }

    public final CustomersTaskContext getCustomersTaskContext() {
        return customersTaskContext;
    }
}

public class PrintCustomer {

    private PrintCustomersContext printCustomersContext;

    public PrintCustomer(PrintCustomersContext pcc) {
        this.printCustomersContext = pcc;
    }

    public final void printCustomer(Customer customer) {
        System.out.println(customer.getName());
    }
}

public class CustomerData {

    private LinkedList customerList;

    public CustomerData() {
        customerList = new LinkedList();
    }

    public boolean addCustomer(Customer c) {
        return getCustomerList().add(c);
    }

    public LinkedList getCustomerList() {
        return customerList;
    }
}

public class Customer {

    private String name;

    public Customer(String name) {
        this.name = name;
    }

    public String getName() {
        return name;
    }
}