Sample of Java Pattern -- Proxy

Order.java

package proxy;

import java.io.Serializable;
import java.util.Date;

public class Order implements Serializable {

    private int orderId;
    private String sku;
    private Date createdOn;
    private Date updatedOn;
    private int status;
    
    public int getOrderId() {
        return orderId;
    }
    public void setOrderId(int orderId) {
        this.orderId = orderId;
    }
    public String getSku() {
        return sku;
    }
    public void setSku(String sku) {
        this.sku = sku;
    }
    public Date getCreatedOn() {
        return createdOn;
    }
    public void setCreatedOn(Date createdOn) {
        this.createdOn = createdOn;
    }
    public Date getUpdatedOn() {
        return updatedOn;
    }
    public void setUpdatedOn(Date updatedOn) {
        this.updatedOn = updatedOn;
    }
    public int getStatus() {
        return status;
    }
    public void setStatus(int status) {
        this.status = status;
    }
    @Override
    public int hashCode() {
        final int prime = 31;
        int result = 1;
        result = prime * result + ((sku == null) ? 0 : sku.hashCode());
        return result;
    }
    @Override
    public boolean equals(Object obj) {
        if (this == obj)
            return true;
        if (obj == null)
            return false;
        if (getClass() != obj.getClass())
            return false;
        Order other = (Order) obj;
        if (sku == null) {
            if (other.sku != null)
                return false;
        } else if (!sku.equals(other.sku))
            return false;
        return true;
    }
}

OrderDAO.java

package proxy;

import java.util.List;

public interface OrderDAO {
    public List<Order> getAllOrders();
}

OrderDAOImpl.java

package proxy;

import java.util.ArrayList;
import java.util.List;

public class OrderDAOImpl implements OrderDAO{
    public List<Order> getAllOrders(){
        List<Order> list = new ArrayList<Order>();
        for(int i =0; i<10; i++){
            Order order = new Order();
            order.setSku("sku"+i);
            list.add(order);
        }
        return list;
    }
}

OrderDAOProxy.java

package proxy;

import java.util.List;

public class OrderDAOProxy implements OrderDAO{
    public List<Order> getAllOrders(){
        long stTime = System.currentTimeMillis();
        OrderDAO orderDAOImpl = new OrderDAOImpl();
        List<Order> list = orderDAOImpl.getAllOrders();
        long endTime = System.currentTimeMillis();
        System.out.println("took " + (endTime - stTime) + " milliseconds.");
        return list;
    }
}

ProxyTest.java

package proxy;

public class ProxyTest {

    public static void main(String[] args) {
        OrderDAO orderDAOProxy = new OrderDAOProxy();
        orderDAOProxy.getAllOrders();
    }

}

you may download the source code.

Sample of Java Pattern -- State

OrderState.java

package state;

public interface OrderState {
    public void handleOrder(String orderNo);
    public void cancelOrder(String orderNo);
    public void completeOrder(String orderNo);
}

OrderOpendState.java

package state;

public class OrderOpendState implements OrderState {
    
    OrderStateMgmt orderStateMgmt;
    
    public OrderOpendState(OrderStateMgmt orderStateMgmt){
        this.orderStateMgmt = orderStateMgmt;
    }
    
    public void handleOrder(String orderNo){
        System.out.println("handle this order, orderNo=" + orderNo);
        orderStateMgmt.setState(orderStateMgmt.getOrderInProgressState());
    }
    
    public void cancelOrder(String orderNo){
        System.out.println("cancel this order, orderNo=" + orderNo);
        orderStateMgmt.setState(orderStateMgmt.getOrderCancelledState());
    }
    
    public void completeOrder(String orderNo){
        System.out.println("could not complete this order under opend status, orderNo=" + orderNo);
    }
}

OrderInProgressState.java

package state;

public class OrderInProgressState implements OrderState {
    
    OrderStateMgmt orderStateMgmt;
    
    public OrderInProgressState(OrderStateMgmt orderStateMgmt){
        this.orderStateMgmt = orderStateMgmt;
    }
    
    public void handleOrder(String orderNo){
        System.out.println("could not handle this order under in progress status, orderNo=" + orderNo);
    }
    
    public void cancelOrder(String orderNo){
        System.out.println("cancel this order, orderNo=" + orderNo);
        orderStateMgmt.setState(orderStateMgmt.getOrderCancelledState());
    }
    
    public void completeOrder(String orderNo){
        System.out.println("complete this order, orderNo=" + orderNo);
        orderStateMgmt.setState(orderStateMgmt.getOrderClosedState());
    }
}

OrderCancelledState.java

package state;

public class OrderCancelledState implements OrderState {
    
    OrderStateMgmt orderStateMgmt;
    
    public OrderCancelledState(OrderStateMgmt orderStateMgmt){
        this.orderStateMgmt = orderStateMgmt;
    }
    
    public void handleOrder(String orderNo){
        System.out.println("could not handle this order under cancelled status, orderNo=" + orderNo);
    }
    
    public void cancelOrder(String orderNo){
        System.out.println("could not cancel this order under cancelled status, orderNo=" + orderNo);
    }
    
    public void completeOrder(String orderNo){
        System.out.println("could not complete this order under cancelled status, orderNo=" + orderNo);
    }
}

OrderClosedState.java

package state;

public class OrderClosedState implements OrderState {
    
    OrderStateMgmt orderStateMgmt;
    
    public OrderClosedState(OrderStateMgmt orderStateMgmt){
        this.orderStateMgmt = orderStateMgmt;
    }
    
    public void handleOrder(String orderNo){
        System.out.println("could not handle this order under closed status, orderNo=" + orderNo);
    }
    
    public void cancelOrder(String orderNo){
        System.out.println("could not cancel this order under closed status, orderNo=" + orderNo);
    }
    
    public void completeOrder(String orderNo){
        System.out.println("could not complete this order under closed status, orderNo=" + orderNo);
    }
}

OrderStateMgmt.java

package state;

public class OrderStateMgmt {
    
    private OrderOpendState orderOpendState;
    private OrderInProgressState orderInProgressState;
    private OrderCancelledState orderCancelledState;
    private OrderClosedState orderClosedState;
    
    private OrderState orderState;
    
    public OrderStateMgmt(){
        this.orderOpendState = new OrderOpendState(this);
        this.orderInProgressState = new OrderInProgressState(this);
        this.orderCancelledState = new OrderCancelledState(this);
        this.orderClosedState = new OrderClosedState(this);
        this.orderState = this.orderOpendState;
        System.out.println("The order inital status is: opend.");
    }
    
    public void setState(OrderState orderState){
        this.orderState = orderState;
    }

    public OrderOpendState getOrderOpendState() {
        return orderOpendState;
    }

    public OrderInProgressState getOrderInProgressState() {
        return orderInProgressState;
    }

    public OrderCancelledState getOrderCancelledState() {
        return orderCancelledState;
    }

    public OrderClosedState getOrderClosedState() {
        return orderClosedState;
    }

    public void handleOrder(String orderNo){
        orderState.handleOrder(orderNo);
    }
    
    public void cancelOrder(String orderNo){
        orderState.cancelOrder(orderNo);
    }
    
    public void completeOrder(String orderNo){
        orderState.completeOrder(orderNo);
    }
}

OrderStateTest.java

package state;

public class OrderStateTest {

    public static void main(String[] args) {
        OrderStateMgmt orderStateMgmtA = new OrderStateMgmt();
        
        orderStateMgmtA.handleOrder("01");
        orderStateMgmtA.completeOrder("01");

        OrderStateMgmt orderStateMgmtB = new OrderStateMgmt();

        orderStateMgmtB.handleOrder("02");
        orderStateMgmtB.cancelOrder("02");
        
        OrderStateMgmt orderStateMgmtC = new OrderStateMgmt();

        orderStateMgmtC.completeOrder("03");
    }

}

you may download the source code.

Sample of Java Pattern -- Composite

Department.java

package composite;

import java.util.List;

public interface Department {
    public Department getDepartment();
    public String getDepartmentname();
    public void add(Department department);
    public void remove(Department department);
    public boolean hasSubDepartments();
    public List<Department> getSubDepartments();
}

CompositeDepartment.java

package composite;

import java.util.ArrayList;
import java.util.List;

public class CompositeDepartment implements Department {
    private String name;
    private List<Department> departments = new ArrayList<Department>();
    
    public CompositeDepartment(String name) {
        super();
        System.out.println("Department " + name + " is created.");
        this.name = name;
    }

    public Department getDepartment() {
        return this;
    }

    public String getDepartmentname() {
        return this.name;
    }
    
    public void add(Department department){
        System.out.println("Department " + department.getDepartmentname() + " is added to Department " + this.name + ".");
        departments.add(department);
    }

    public void remove(Department department){
        System.out.println("Department " + department.getDepartmentname() + " is removed from Department " + this.name + ".");
        departments.remove(department);
    }

    public boolean hasSubDepartments(){
        if(departments == null || departments.isEmpty())
            return false;
        return true;
    }
    
    public List<Department> getSubDepartments(){
        if(hasSubDepartments())
            return departments;
        return null;
    }
}

SingleDepartment.java

package composite;

import java.util.List;

public class SingleDepartment implements Department {
    private String name;
    
    public SingleDepartment(String name) {
        super();
        System.out.println("Department " + name + " is created.");
        this.name = name;
    }

    public Department getDepartment() {
        return this;
    }

    public String getDepartmentname() {
        return this.name;
    }

    public void add(Department department){
        System.out.println("Could not add a child department in Department " + this.name + ".");
    }

    public void remove(Department department){
        System.out.println("Department " + department.getDepartmentname() + " doesn't belong to Department " + this.name + ".");
    }
    
    public boolean hasSubDepartments(){
        return false;
    }
    
    public List<Department> getSubDepartments(){
        return null;
    }
}

CompositeTest.java

package composite;

public class CompositeTest {
    public static void main(String[] args) {
        Department hq = new CompositeDepartment("HQ");
        Department financing = new SingleDepartment("Financing");
        Department marketing = new CompositeDepartment("Marketing");
        Department preSales = new SingleDepartment("PreSales");
        Department sales = new SingleDepartment("Sales");
        Department postSales = new SingleDepartment("PostSales");
        Department techSupport = new SingleDepartment("TechSupport");
        hq.add(financing);
        hq.add(marketing);
        hq.add(techSupport);
        marketing.add(preSales);
        marketing.add(sales);
        marketing.add(postSales);
        System.out.println("hq has sub departments: " + hq.hasSubDepartments());
        System.out.println("marketing has sub departments: " + marketing.hasSubDepartments());
        System.out.println("techSupport has sub departments: " + techSupport.hasSubDepartments());
        marketing.remove(preSales);
        marketing.remove(sales);
        marketing.remove(postSales);
        sales.remove(preSales);
        hq.remove(financing);
        hq.remove(marketing);
        hq.remove(techSupport);
    }
}

you may download the source code.

Sample of Java Pattern -- Iterator

Aggregate.java

package iterator;

public interface Aggregate {
    public abstract Iterator iterator();
}

Iterator.java

package iterator;

public interface Iterator {
    public abstract boolean hasNext();  
    public abstract Object next();  
}

Order.java

package iterator;

import java.util.Date;

public class Order {
    private String name;
    private Date createdOn = new Date();
    private Date updatedOn = new Date();
    
    public Order(String name) {
        super();
        this.name = name;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public Date getCreatedOn() {
        return createdOn;
    }
    public void setCreatedOn(Date createdOn) {
        this.createdOn = createdOn;
    }
    public Date getUpdatedOn() {
        return updatedOn;
    }
    public void setUpdatedOn(Date updatedOn) {
        this.updatedOn = updatedOn;
    }
}

Orders.java

package iterator;

import java.util.Date;

public class Orders implements Aggregate{
    private Order[] orders;
    private int last = 0;
    
    public Orders(int max){
        this.orders = new Order[max];
    }
    
    public Order getOrderAt(int index){
        return this.orders[index];
    }
    
    public void appendOrder(Order order){
        this.orders[last] = order;
        this.last ++ ;
    }
    
    public int getLength(){
        return orders.length;
    }
    
    public Iterator iterator() {
        return new OrdersIterator(this);
    }
}

OrdersIterator.java

package iterator;

public class OrdersIterator implements Iterator{
    private Orders orders;
    private int index;
    
    public OrdersIterator(Orders orders) {
        this.orders = orders;
        this.index = 0;
    }
    
    public boolean hasNext(){
        if(index < orders.getLength()){
            return true;
        }else{
            return false;
        }
    }
    
    public Order next(){
        Order order = orders.getOrderAt(this.index);
        this.index ++ ;
        return order;
    }
}

IteratorTest.java

package iterator;

public class IteratorTest {

    public static void main(String[] args) {
        Orders orders = new Orders(3);
        orders.appendOrder(new Order("order1"));
        orders.appendOrder(new Order("order2"));
        orders.appendOrder(new Order("order3"));
        Iterator iterator = orders.iterator();
        while(iterator.hasNext()) {
            Order order = (Order)iterator.next();
            System.out.println(order.getName());
        }
    }

}

you may download the source code.

Sample of Java Pattern -- Template Method

EmailTemplate.java

package templatemethod;

import javax.mail.*;
import javax.mail.internet.*;

public abstract class EmailTemplate {
    public void send(String smtpHostName, String smtpPort, String smtpAuthUser, String smtpAuthPwd, String[] recipients, String subject,String message, String from){
        MimeMessage msg = connect(smtpHostName, smtpPort, smtpAuthUser, smtpAuthPwd);
        try {
            InternetAddress addressFrom = new InternetAddress(from);
            msg.setFrom(addressFrom);

            InternetAddress[] addressTo = new InternetAddress[recipients.length];
            for (int i = 0; i < recipients.length; i++) {
                addressTo[i] = new InternetAddress(recipients[i]);
            }
            msg.setRecipients(Message.RecipientType.TO, addressTo);

            msg.setSubject(subject);
            msg.setContent(message, "text/html");
            Transport.send(msg);
        } catch (MessagingException e) {
            System.out.println("Could not send this email, title=" + subject + " addressTo=" + recipients[0] + ", please check the email server connection.");
        }
    }
    
    protected abstract MimeMessage connect(String smtpHostName, String smtpPort, String smtpAuthUser, String smtpAuthPwd);
}

GeneralEmailService.java

package templatemethod;

import java.security.Security;
import java.util.Properties;

import javax.mail.Authenticator;
import javax.mail.Session;
import javax.mail.internet.MimeMessage;

import templatemethod.GoogleEmailService.SMTPAuthenticator;

public class GeneralEmailService extends EmailTemplate{
    private String smtpAuthUser;
    private String smtpAuthPwd;
    protected MimeMessage connect(String smtpHostName, String smtpPort, String smtpAuthUser, String smtpAuthPwd){
        
        this.smtpAuthUser = smtpAuthUser;
        this.smtpAuthPwd = smtpAuthPwd;
        
        boolean debug = false;

        Properties props = new Properties();
        props.setProperty("mail.transport.protocol", "smtp");
        props.setProperty("mail.host", smtpHostName);
        props.put("mail.smtp.auth", "true");
        props.put("mail.smtp.port", smtpPort);
        props.setProperty("mail.smtp.quitwait", "false");

        Authenticator auth = new SMTPAuthenticator();
        Session session = Session.getDefaultInstance(props, auth);

        session.setDebug(debug);

        MimeMessage msg = new MimeMessage(session);
        
        return msg;
        
    }
    
    private class SMTPAuthenticator extends javax.mail.Authenticator {
        public PasswordAuthentication getPasswordAuthentication() {
            String username = smtpAuthUser;
            String password = smtpAuthPwd;
            return new PasswordAuthentication(username, password);
        }
    }


}

GoogleEmailService.java

package templatemethod;

import java.security.Security;
import java.util.Properties;

import javax.mail.Authenticator;
import javax.mail.PasswordAuthentication;
import javax.mail.Session;
import javax.mail.internet.MimeMessage;

public class GoogleEmailService extends EmailTemplate{
    private String smtpAuthUser;
    private String smtpAuthPwd;
    protected MimeMessage connect(String smtpHostName, String smtpPort, String smtpAuthUser, String smtpAuthPwd){
        
        this.smtpAuthUser = smtpAuthUser;
        this.smtpAuthPwd = smtpAuthPwd;
        
        boolean debug = false;

        Security.addProvider(new com.sun.net.ssl.internal.ssl.Provider());

        Properties props = new Properties();
        props.setProperty("mail.transport.protocol", "smtp");
        props.setProperty("mail.host", smtpHostName);
        props.put("mail.smtp.auth", "true");
        props.put("mail.smtp.port", smtpPort);
        props.setProperty("mail.smtp.quitwait", "false");

        props.put("mail.smtp.socketFactory.port", smtpPort);
        props.put("mail.smtp.socketFactory.class","javax.net.ssl.SSLSocketFactory");
        props.put("mail.smtp.socketFactory.fallback", "false");

        Authenticator auth = new SMTPAuthenticator();
        Session session = Session.getDefaultInstance(props, auth);

        session.setDebug(debug);

        MimeMessage msg = new MimeMessage(session);
        
        return msg;
        
    }
    
    private class SMTPAuthenticator extends javax.mail.Authenticator {
        public PasswordAuthentication getPasswordAuthentication() {
            String username = smtpAuthUser;
            String password = smtpAuthPwd;
            return new PasswordAuthentication(username, password);
        }
    }

}

TemplateMethodTest.java

package templatemethod;

public class TemplateMethodTest {

    public static void main(String[] args) {
        String smtpHostName = "";
        String smtpPort = "";
        String smtpAuthUser = "";
        String smtpAuthPwd = "";
        String[] recipients = {""};
        String subject = "";
        String message = "";
        String from = "";
        EmailTemplate googleEmailService = new GoogleEmailService();
        googleEmailService.send(smtpHostName, smtpPort, smtpAuthUser, smtpAuthPwd, recipients, subject, message, from);
        EmailTemplate generalEmailService = new GeneralEmailService();
        generalEmailService.send(smtpHostName, smtpPort, smtpAuthUser, smtpAuthPwd, recipients, subject, message, from);
    }

}

you may download the source code.

Sample of Java Pattern -- Façade

Customer.java

package facade;

public class Customer {
    private String name;
    private String address;
    private Order order;
    
    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }
    
    public Order getOrder() {
        return order;
    }

    public void setOrder(Order order) {
        this.order = order;
    }
    
    public void save(){
        
    }

}

Order.java

package facade;

public class Order {
    private String sku;

    public String getSku() {
        return sku;
    }

    public void setSku(String sku) {
        this.sku = sku;
    }
    
    public void save(){
        
    }
}

CustomerFacade.java

package facade;

public class CustomerFacade {
    public void placeOrder(String customerName, String customerAddress, String sku){
        Customer customer = new Customer();
        customer.setName(customerName);
        customer.setAddress(customerAddress);
        Order order = new Order();
        order.setSku(sku);
        customer.setOrder(order);
        customer.save();
        order.save();
    }
}

FacadeTest.java

package facade;

public class FacadeTest {

    public static void main(String[] args) {
        CustomerFacade customerFacade = new CustomerFacade();
        customerFacade.placeOrder("customerName", "customerAddress", "sku");
    }

}

you may download the source code.

Sample of Java Pattern -- Adapter

LegacyModel.java

package adapter;

public class LegacyModel {
    public void ins(String sku){
        System.out.println("call ins method.");
    }
}

ModernModel.java

package adapter;

public interface ModernModel {
    public void save(Order order);
}

ModernModelAdapter.java

package adapter;

public class ModernModelAdapter implements ModernModel{
    private LegacyModel legacyModel;
    
    public ModernModelAdapter(LegacyModel legacyModel) {
        super();
        this.legacyModel = legacyModel;
    }
    
    public void save(Order order){
        String sku = order.getSku();
        legacyModel = new LegacyModel();
        legacyModel.ins(sku);
    }
}

Order.java

package adapter;

public class Order {
    private String sku;

    public String getSku() {
        return sku;
    }

    public void setSku(String sku) {
        this.sku = sku;
    }
    
}

AdapterTest.java

package adapter;

public class AdapterTest {
    public static void main(String[] args) {
        LegacyModel legacy = new LegacyModel(); 
        Order order = new Order();
        order.setSku("sku");
        ModernModelAdapter adapter = new ModernModelAdapter(legacy);
        adapter.save(order);
    }
}

you may download the source code.

Sample of Java Pattern -- Command

Command.java

package command;

public interface Command {
  public void execute();
}

ConfirmCommand.java

package command;

public class ConfirmCommand implements Command {

  private EmailService emailService;

  public ConfirmCommand(){}

  public void execute() {
      emailService = new EmailService();
      emailService.confirmMeeting();
  }

}

CancelCommand.java

package command;

public class CancelCommand implements Command {

  private EmailService emailService;

  public CancelCommand(){}

  public void execute() {
      emailService = new EmailService();
      emailService.cancelMeeting();
  }

}

EmailService.java

package command;

public class EmailService {

  public EmailService(){}

  public void cancelMeeting(){
      System.out.println("send cacellation email");
  }

  public void confirmMeeting(){
      System.out.println("send confirmation email");
  }

}

Invoker.java

package command;

public class Invoker {
  private Command command;

  public Invoker(){
  }

  public void setCommand(Command command){
      this.command = command;
  }

  public void executeCommand(){
      this.command.execute();
  }
}

CommandTest.java

package command;

public class CommandTest {

  public static void main(String[] args) {
      CancelCommand cancelCommand = new CancelCommand();
      ConfirmCommand confirmCommand = new ConfirmCommand();
      Invoker invoker = new Invoker();
      invoker.setCommand(confirmCommand);
      invoker.executeCommand();
      invoker.setCommand(cancelCommand);
      invoker.executeCommand();
  }

}

you can download the source code .

Sample of Java Pattern -- Singleton

Utils.java

package singleton;

public class Utils {
    
    private Utils(){}
    
    private static Utils instance = new Utils();
    
    public static Utils getInstance() {
        return instance;
    }
    
    public void println(String str){
        System.out.println(str);
    }

    public static void main(String[] args) {
        Utils.getInstance().println("Hello");
    }
}

you may download the source code.

Sample of Java Pattern -- Factory

Customer.java

package factory;

import java.io.Serializable;
import java.util.Date;
import java.util.HashSet;
import java.util.Set;

public class Customer implements Serializable {

    private Long customerId;
    private String firstName;
    private String lastName;
    private String address;
    private String city;
    private String postalCode;
    private String workPhone;
    private String homePhone;
    private String cellPhone;
    private String email;
    private Date createdOn;
    private Date updatedOn;
    private Set<Order> orders = new HashSet<Order>(0);
    
    public Long getCustomerId() {
        return customerId;
    }
    public void setCustomerId(Long customerId) {
        this.customerId = customerId;
    }
    public String getFirstName() {
        return firstName;
    }
    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }
    public String getLastName() {
        return lastName;
    }
    public void setLastName(String lastName) {
        this.lastName = lastName;
    }
    public String getAddress() {
        return address;
    }
    public void setAddress(String address) {
        this.address = address;
    }
    public String getCity() {
        return city;
    }
    public void setCity(String city) {
        this.city = city;
    }
    public String getPostalCode() {
        return postalCode;
    }
    public void setPostalCode(String postalCode) {
        this.postalCode = postalCode;
    }
    public String getWorkPhone() {
        return workPhone;
    }
    public void setWorkPhone(String workPhone) {
        this.workPhone = workPhone;
    }
    public String getHomePhone() {
        return homePhone;
    }
    public void setHomePhone(String homePhone) {
        this.homePhone = homePhone;
    }
    public String getCellPhone() {
        return cellPhone;
    }
    public void setCellPhone(String cellPhone) {
        this.cellPhone = cellPhone;
    }
    public String getEmail() {
        return email;
    }
    public void setEmail(String email) {
        this.email = email;
    }
    public Date getCreatedOn() {
        return createdOn;
    }
    public void setCreatedOn(Date createdOn) {
        this.createdOn = createdOn;
    }
    public Date getUpdatedOn() {
        return updatedOn;
    }
    public void setUpdatedOn(Date updatedOn) {
        this.updatedOn = updatedOn;
    }
    public Set<Order> getOrders() {
        return orders;
    }
    public void setOrders(Set<Order> orders) {
        this.orders = orders;
    }
    @Override
    public int hashCode() {
        final int prime = 31;
        int result = 1;
        result = prime * result + ((email == null) ? 0 : email.hashCode());
        return result;
    }
    @Override
    public boolean equals(Object obj) {
        if (this == obj)
            return true;
        if (obj == null)
            return false;
        if (getClass() != obj.getClass())
            return false;
        Customer other = (Customer) obj;
        if (email == null) {
            if (other.email != null)
                return false;
        } else if (!email.equals(other.email))
            return false;
        return true;
    }

}

Order.java

package factory;

import java.io.Serializable;
import java.util.Date;

public class Order implements Serializable {

    private int orderId;
    private Customer customer;
    private String sku;
    private Date createdOn;
    private Date updatedOn;
    private int status;
    
    public int getOrderId() {
        return orderId;
    }
    public void setOrderId(int orderId) {
        this.orderId = orderId;
    }
    public Customer getCustomer() {
        return customer;
    }
    public void setCustomer(Customer customer) {
        this.customer = customer;
    }
    public String getSku() {
        return sku;
    }
    public void setSku(String sku) {
        this.sku = sku;
    }
    public Date getCreatedOn() {
        return createdOn;
    }
    public void setCreatedOn(Date createdOn) {
        this.createdOn = createdOn;
    }
    public Date getUpdatedOn() {
        return updatedOn;
    }
    public void setUpdatedOn(Date updatedOn) {
        this.updatedOn = updatedOn;
    }
    public int getStatus() {
        return status;
    }
    public void setStatus(int status) {
        this.status = status;
    }
    @Override
    public int hashCode() {
        final int prime = 31;
        int result = 1;
        result = prime * result + ((sku == null) ? 0 : sku.hashCode());
        return result;
    }
    @Override
    public boolean equals(Object obj) {
        if (this == obj)
            return true;
        if (obj == null)
            return false;
        if (getClass() != obj.getClass())
            return false;
        Order other = (Order) obj;
        if (sku == null) {
            if (other.sku != null)
                return false;
        } else if (!sku.equals(other.sku))
            return false;
        return true;
    }
}

DomainObjMgmt.java

package factory;

import java.util.Date;

public class DomainObjMgmt {
    public static Object create(String which){
        Object obj = null;
        if (which.equalsIgnoreCase("customer")) {
            Customer customer = new Customer();
            customer.setFirstName("firstName");
            customer.setLastName("lastName");
            customer.setAddress("address");
            customer.setCity("city");
            customer.setPostalCode("postalCode");
            customer.setWorkPhone("workPhone");
            customer.setHomePhone("homePhone");
            customer.setCellPhone("cellPhone");
            customer.setEmail("email");
            customer.setCreatedOn(new Date());
            customer.setUpdatedOn(new Date());
            obj = customer;
            System.out.println("Creating a customer, done.");
        }else if(which.equalsIgnoreCase("order")){
            Order order = new Order();
            order.setSku("sku");
            order.setCreatedOn(new Date());
            order.setUpdatedOn(new Date());
            obj = order;
            System.out.println("Creating an order, done.");
        }else{
            obj = null;
            System.out.println("Could not create this object");
        }
        return obj;
    }
}

FactoryTest.java

package factory;

public class FactoryTest {
    public static void main(String[] args) {
        Customer customer = (Customer)DomainObjMgmt.create("customer"); 
        Order order = (Order)DomainObjMgmt.create("order"); 
        DomainObjMgmt.create("advisor"); 
    }
}

you may download the source code.

Sample of Java Pattern -- Observer

Appointment.java

package observer;

import java.util.Date;
import java.util.Observable;

public class Appointment extends Observable {
    private String host;
    private String guest;
    private Date appointmentDate;
    private int status;
    
    public Appointment(){}
    
    public String getHost() {
        return host;
    }

    public String getGuest() {
        return guest;
    }

    public Date getAppointmentDate() {
        return appointmentDate;
    }

    public int getStatus() {
        return status;
    }

    public void createAppointment(String host, String guest, Date appointmentDate){
        this.host = host;
        this.guest = guest;
        this.appointmentDate = appointmentDate;
        this.status = 0;
        setChanged();
        this.notifyObservers(this);
    }

    public void cancelAppointment(String host, String guest, Date appointmentDate){
        if(this.host != null && this.guest != null && this.appointmentDate != null && this.status != 1){
            this.status = 1;
            setChanged();
            this.notifyObservers(this);
        }
    }

}

EmailService.java

package observer;

import java.util.Observable;
import java.util.Observer;

public class EmailService implements Observer {
    private Observable observable;
    
    public EmailService(Observable observable){
        this.observable = observable;
        observable.addObserver(this);
    }
    
    public void update(Observable o, Object arg) {
        if(arg instanceof Appointment){
            Appointment appointment = (Appointment)arg;
            if(appointment.getStatus() ==0)
                System.out.println("send a creation email to host and guest");
            else
                System.out.println("send a cancellation email to host and guest");
        }
    }

}

SMSService.java

package observer;

import java.util.Observable;
import java.util.Observer;

public class SMSService implements Observer {
    private Observable observable;
    
    public SMSService(Observable observable){
        this.observable = observable;
        observable.addObserver(this);
    }
    
    public void update(Observable o, Object arg) {
        if(arg instanceof Appointment){
            Appointment appointment = (Appointment)arg;
            if(appointment.getStatus() ==0)
                System.out.println("send a creation sms to host and guest");
            else
                System.out.println("send a cancellation sms to host and guest");
        }
    }
}

ObserverTest.java

package observer;

import java.util.Date;

public class ObserverTest {

    public static void main(String[] args) {
        Appointment appointment = new Appointment();
        EmailService emailService = new EmailService(appointment);
        SMSService smsService = new SMSService(appointment);
        String host ="";
        String guest ="";
        Date appointmentDate = new Date();
        appointment.createAppointment(host, guest, appointmentDate);
        appointment.cancelAppointment(host, guest, appointmentDate);
    }

}

you may download the source code.

sample of Java Pattern -- Strategy

Intent
Define a family of algorithms, encapsulate each one, and make them interchangeable. Strategy lets the algorithm vary independently from clients that use it.

Type
Object Behavioral

Solution
The Strategy Pattern is one of the less complex patterns defined by the Gang of Four. The Strategy Pattern first identifies the behaviors or algorithms that vary and separate them from the system that stays the same. These behaviors or algorithms are encapsulated in classes that implement a common interface. This enables the developer to program to an interface and not an implementation. The different algorithms are encapsulated in a concrete class (ConcreteStrategy). Each of these objects are referenced by classes (Context) through the common interface (Strategy).

Class Diagram Example


Java Sample Code
EmailService.java

package strategy;

public interface EmailService {
    public void send(String[] recipients, String subject, String message, String from);
}

GeneralEmailServiceImpl.java

package strategy;

import java.util.Properties;

import javax.mail.Authenticator;
import javax.mail.Message;
import javax.mail.MessagingException;
import javax.mail.PasswordAuthentication;
import javax.mail.Session;
import javax.mail.Transport;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeMessage;

public class GeneralEmailServiceImpl implements EmailService {
    private String smtpHostName;
    private String smtpPort;
    private String smtpAuthUser;
    private String smtpAuthPwd;
    
    public String getSmtpHostName() {
        return smtpHostName;
    }

    public String getSmtpPort() {
        return smtpPort;
    }

    public String getSmtpAuthUser() {
        return smtpAuthUser;
    }

    public String getSmtpAuthPwd() {
        return smtpAuthPwd;
    }

    public GeneralEmailServiceImpl(String smtpHostName, String smtpPort, String smtpAuthUser, String smtpAuthPwd){
        this.smtpHostName = smtpHostName;
        this.smtpPort = smtpPort;
        this.smtpAuthUser = smtpAuthUser;
        this.smtpAuthPwd = smtpAuthPwd;
    }
    
    public void send(String[] recipients, String subject, String message, String from) {
        boolean debug = false;

        Properties props = new Properties();
        props.setProperty("mail.transport.protocol", "smtp");
        props.setProperty("mail.host", getSmtpHostName());
        props.put("mail.smtp.auth", "true");
        props.put("mail.smtp.port", getSmtpPort());
        props.setProperty("mail.smtp.quitwait", "false");

        Authenticator auth = new SMTPAuthenticator();
        Session session = Session.getDefaultInstance(props, auth);

        session.setDebug(debug);

        MimeMessage msg = new MimeMessage(session);

        try {
            InternetAddress addressFrom = new InternetAddress(from);
            msg.setFrom(addressFrom);

            InternetAddress[] addressTo = new InternetAddress[recipients.length];
            for (int i = 0; i < recipients.length; i++) {
                addressTo[i] = new InternetAddress(recipients[i]);
            }
            msg.setRecipients(Message.RecipientType.TO, addressTo);

            msg.setSubject(subject);
            msg.setContent(message, "text/html");
            Transport.send(msg);
        } catch (MessagingException e) {
            e.printStackTrace();
            return;
        }
    }

    private class SMTPAuthenticator extends javax.mail.Authenticator {
        public PasswordAuthentication getPasswordAuthentication() {
            String username = getSmtpAuthUser();
            String password = getSmtpAuthPwd();
            return new PasswordAuthentication(username, password);
        }
    }

}

GoogleEmailServiceImpl.java

package strategy;

import java.security.Security;
import java.util.Properties;

import javax.mail.Authenticator;
import javax.mail.Message;
import javax.mail.MessagingException;
import javax.mail.PasswordAuthentication;
import javax.mail.Session;
import javax.mail.Transport;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeMessage;

public class GoogleEmailServiceImpl implements EmailService {
    private String smtpHostName;
    private String smtpPort;
    private String smtpAuthUser;
    private String smtpAuthPwd;
    
    public String getSmtpHostName() {
        return smtpHostName;
    }

    public String getSmtpPort() {
        return smtpPort;
    }

    public String getSmtpAuthUser() {
        return smtpAuthUser;
    }

    public String getSmtpAuthPwd() {
        return smtpAuthPwd;
    }

    public GoogleEmailServiceImpl(String smtpHostName, String smtpPort, String smtpAuthUser, String smtpAuthPwd){
        this.smtpHostName = smtpHostName;
        this.smtpPort = smtpPort;
        this.smtpAuthUser = smtpAuthUser;
        this.smtpAuthPwd = smtpAuthPwd;
    }
    
    public void send(String[] recipients, String subject, String message, String from) {
        boolean debug = false;

        Security.addProvider(new com.sun.net.ssl.internal.ssl.Provider());

        Properties props = new Properties();
        props.setProperty("mail.transport.protocol", "smtp");
        props.setProperty("mail.host", getSmtpHostName());
        props.put("mail.smtp.auth", "true");
        props.put("mail.smtp.port", getSmtpPort());
        props.setProperty("mail.smtp.quitwait", "false");
        props.put("mail.smtp.socketFactory.port", getSmtpPort());
        props.put("mail.smtp.socketFactory.class","javax.net.ssl.SSLSocketFactory");
        props.put("mail.smtp.socketFactory.fallback", "false");

        Authenticator auth = new SMTPAuthenticator();
        Session session = Session.getDefaultInstance(props, auth);

        session.setDebug(debug);

        MimeMessage msg = new MimeMessage(session);

        try {
            InternetAddress addressFrom = new InternetAddress(from);
            msg.setFrom(addressFrom);

            InternetAddress[] addressTo = new InternetAddress[recipients.length];
            for (int i = 0; i < recipients.length; i++) {
                addressTo[i] = new InternetAddress(recipients[i]);
            }
            msg.setRecipients(Message.RecipientType.TO, addressTo);

            msg.setSubject(subject);
            msg.setContent(message, "text/html");
            Transport.send(msg);
        } catch (MessagingException e) {
            e.printStackTrace();
        }
    }

    private class SMTPAuthenticator extends javax.mail.Authenticator {
        public PasswordAuthentication getPasswordAuthentication() {
            String username = getSmtpAuthUser();
            String password = getSmtpAuthPwd();
            return new PasswordAuthentication(username, password);
        }
    }


}

EmailServiceSelectorTest.java

package strategy;

public class EmailServiceSelectorTest {

    public static void main(String[] args) {
        String smtpHostName = "";
        String smtpPort = "";
        String smtpAuthUser = "";
        String smtpAuthPwd = "";
        String[] recipients = {""}; 
        String subject = "";
        String message = "";
        String from = "";
        GoogleEmailServiceImpl googleEmailServiceImpl = new GoogleEmailServiceImpl(smtpHostName, smtpPort, smtpAuthUser, smtpAuthPwd);
        GeneralEmailServiceImpl generalEmailServiceImpl = new GeneralEmailServiceImpl(smtpHostName, smtpPort, smtpAuthUser, smtpAuthPwd);
        googleEmailServiceImpl.send(recipients, subject, message, from);
        generalEmailServiceImpl.send(recipients, subject, message, from);
    }

}

you may download the source code.