Factory Method模式可以由Template Method演变而来。用Template Method模式来构建生成实例的工厂，这就是Factory Method。
在Factory Method模式中，父类决定实例的生成方式，但是不决定具体要生成的类，具体的处理全部交给子类去负责。这样就可以将生成实例的框架（framework）和实际负责生成实例的类解耦。
类图
示例代码
Product（之定义抽象方法use的抽象类）
/**
* 只定义抽象方法use的抽象类
*
* Created by xuefeihu on 18/4/12.
*/
public abstract class Product {
public abstract void use();
}
Factory（实现了create方法的抽象类）
/**
* 实现了create方法的抽象类
*
* Created by xuefeihu on 18/4/12.
*/
public abstract class Factory {
public final Product create(String owner) {
Product p = createProduct(owner);
registerProduct(p);
return p;
}
protected abstract Product createProduct(String owner);
protected abstract void registerProduct(Product product);
}IDCard（实现了use方法的类）
/**
* 实现use方法的类
*
* Created by xuefeihu on 18/4/12.
*/
public class IDCard extends Product {
private String owner;
IDCard(String owner) {
System.out.println("制作" + owner + "的ID卡.");
this.owner = owner;
}
@Override
public void use() {
System.out.println("使用" + owner + "的ID卡.");
}
public String getOwner() {
return owner;
}
}IDCardFactory（实现了createProduct、registerProduct方法的类）
/**
* 实现了createProduct registerProduct方法的类
*
* Created by xuefeihu on 18/4/12.
*/
public class IDCardFactory extends Factory {
private List owners = new ArrayList();
@Override
protected Product createProduct(String owner) {
return new IDCard(owner);
}
@Override
protected void registerProduct(Product product) {
owners.add(((IDCard) product).getOwner());
}
public List getOwners() {
return owners;
}
}Main（测试入口）
/**
* 测试入口
*
* Created by xuefeihu on 18/4/12.
*/
public class Main {
public static void main(String[] args) {
Factory factory = new IDCardFactory();
Product card1 = factory.create("小明");
Product card2 = factory.create("小红");
Product card3 = factory.create("小刚");
card1.use();
card2.use();
card3.use();
}
}参考：《图解设计模式》
