OnJava8-Examples/generics/decorator/Decoration.java

// generics/decorator/Decoration.java
// (c)2016 MindView LLC: see Copyright.txt
// We make no guarantees that this code is fit for any purpose.
// Visit http://mindviewinc.com/Books/OnJava/ for more book information.
package generics.decorator;
import java.util.*;

class Basic {
  private String value;
  public void set(String val) { value = val; }
  public String get() { return value; }
}

class Decorator extends Basic {
  protected Basic basic;
  public Decorator(Basic basic) { this.basic = basic; }
  @Override
  public void set(String val) { basic.set(val); }
  @Override
  public String get() { return basic.get(); }
}

class TimeStamped extends Decorator {
  private final long timeStamp;
  public TimeStamped(Basic basic) {
    super(basic);
    timeStamp = new Date().getTime();
  }
  public long getStamp() { return timeStamp; }
}

class SerialNumbered extends Decorator {
  private static long counter = 1;
  private final long serialNumber = counter++;
  public SerialNumbered(Basic basic) { super(basic); }
  public long getSerialNumber() { return serialNumber; }
}

public class Decoration {
  public static void main(String[] args) {
    TimeStamped t = new TimeStamped(new Basic());
    TimeStamped t2 = new TimeStamped(
      new SerialNumbered(new Basic()));
    //! t2.getSerialNumber(); // Not available
    SerialNumbered s = new SerialNumbered(new Basic());
    SerialNumbered s2 = new SerialNumbered(
      new TimeStamped(new Basic()));
    //! s2.getStamp(); // Not available
  }
}