public abstract class PenCore{
  String color;
  public abstract void writeWord(String s);
}

public class RedPenCore extends PenCore{
  RedPenCore(){
   color="紅色";
  }
  public void writeWord(String s){
    System.out.println("寫出"+color+"的字:"+s);
  }
}

public class BluePenCore extends PenCore{
  BluePenCore(){
   color="藍色";
  }
  public void writeWord(String s){
    System.out.println("寫出"+color+"的字:"+s);
  }
}

public class BlackPenCore extends PenCore{
  BlackPenCore(){
   color="黑色";
  }
  public void writeWord(String s){
    System.out.println("寫出"+color+"的字:"+s);
  }
}

public abstract class BallPen{
  BallPen(){
    System.out.println("生產(chǎn)了一只裝有"+getPenCore().color+"筆芯的圓珠筆");
  }
  public abstract PenCore getPenCore(); //工廠方法
}

RedBallPen.java
public class RedBallPen extends BallPen{
  public PenCore getPenCore(){
    return new RedPenCore();
  }
}
BlueBallPen.java
public class BlueBallPen extends BallPen{
  public PenCore getPenCore(){
    return new BluePenCore();
  }
}
BlackBallPen.java
public class BlackBallPen extends BallPen{
  public PenCore getPenCore(){
    return new BlackPenCore();
  }
}

public class Application{
  public static void main(String args[]){
    PenCore penCore;
    BallPen ballPen=new BlueBallPen();
    penCore=ballPen.getPenCore();
    penCore.writeWord("你好,很高興認識你");
    ballPen=new RedBallPen();
    penCore=ballPen.getPenCore();
    penCore.writeWord("How are you");
    ballPen=new BlackBallPen();
    penCore=ballPen.getPenCore();
    penCore.writeWord("nice to meet you");
  }
}