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 .