import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.util.ArrayList;

public class CommandLogger {
  public static void main(String[] args) throws Exception {
    //  Write a list of commands for later use
    String fn = "logfile";
    FileOutputStream bytesToDisk = new FileOutputStream(fn);
    ObjectOutputStream objectToBytes = new ObjectOutputStream(bytesToDisk);
    // Imagine commands are some important logged transaction   
    WorkCommand commandWork = new DomesticEngineer();
    WorkCommand commandPol = new Politician();
    WorkCommand commandProg = new Programmer();
    // Create a list to save for later use
    ArrayList<WorkCommand> allCommands = new ArrayList<WorkCommand>();
    allCommands.add(commandWork);
    allCommands.add(commandPol);
    allCommands.add(commandProg); // add more, mix 'em up
    // Save the list to a file for later use
    objectToBytes.writeObject(allCommands);
    objectToBytes.close();

    ///////////////////////////////////////////////////////////
    String fileName = "logfile";
    FileInputStream diskToStreamOfBytes = null;
    ObjectInputStream bytesToObjects = null;

    diskToStreamOfBytes = new FileInputStream(fileName);
    bytesToObjects = new ObjectInputStream(diskToStreamOfBytes);
    ArrayList<WorkCommand> list = (ArrayList<WorkCommand>) bytesToObjects
        .readObject();
    bytesToObjects.close();

    for (WorkCommand command : list)
      command.execute();
  }
}

// Purpose. Command design pattern - decoupling producer from consumer

interface WorkCommand {
  void execute();
}

class DomesticEngineer implements WorkCommand, Serializable {
  public void execute() {
    System.out.println("take out the trash");
  }
}

class Politician implements WorkCommand, Serializable {
  public void execute() {
    System.out.println("take money from the rich, take votes from the poor");
  }
}

class Programmer implements WorkCommand, Serializable {
  public void execute() {
    System.out.println("sell the bugs, charge extra for the fixes");
  }
}