java中工厂模式的优缺点有哪些

package scut.designmodel.SimpleFactoryPattern;//抽象产品类abstract class Product{  public abstract void Show();}//产品A类class ProductA extends Product{  @Override  public void Show() {    System.out.println("生产出了产品A");  }}//产品B类class ProductB extends Product{  @Override  public void Show() {    System.out.println("生产出了产品C");  }}//产品C类class ProductC extends Product{  @Override  public void Show() {    System.out.println("生产出了产品C");  }}//简单工厂类class Factory {  public static Product Manufacture(String ProductName){    switch (ProductName){      case "A":        return new ProductA();      case "B":        return new ProductB();      case "C":        return new ProductC();      default:        return null;    }  }}//工厂产品生产流程public class SimpleFactoryPattern {  public static void main(String[] args){    Factory mFactory = new Factory();    //客户要产品A    try {      mFactory.Manufacture("A").Show();    }catch (NullPointerException e){      System.out.println("没有这一类产品");    }    //客户要产品B    try {      mFactory.Manufacture("B").Show();    }catch (NullPointerException e){      System.out.println("没有这一类产品");    }    //客户要产品C    try {      mFactory.Manufacture("C").Show();    }catch (NullPointerException e){      System.out.println("没有这一类产品");    }    //客户要产品D    try {      mFactory.Manufacture("D").Show();    }catch (NullPointerException e){      System.out.println("没有这一类产品");    }  }}