工厂方法模式

public abstract class Product {
    //产品类的抽象方法
    public abstract void Method1();
    //产品类的公共方法
    public void Method2(){
        System.out.println("abstract Product");
    }
}

public class ConcreteProduct1 extends Product{

    @Override
    public void Method1() {
        // TODO Auto-generated method stub
        
    }

}

public abstract class Creator {
    public abstract <T extends Product> T createProduct(Class<T> c);
}

public class ConcreteCreator extends Creator{

    @Override
    public <T extends Product> T createProduct(Class<T> c) {
        // TODO Auto-generated method stub
        Product product = null;
        try {
            product = (Product)Class.forName(c.getName()).newInstance();
        } catch (InstantiationException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (ClassNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return (T)product;
    }
}

public class Client{
    public static void main(String[] args){
        Creator creator = new ConcreteCreator();
        Product product = creator.createProduct(ConcreteProduct1.class);
        product.Method1();
        product.Method2();
    }
}

public class Singleton {
    private Singleton(){
    }
    public void doSomething(){
    }
}

public class SingletonFactory {
    private static class SingletonHolder{
        private static Singleton singleton;
        static{
            try{
                Class<?> cl = Class.forName(Singleton.class.getName());
                Constructor<?> constructor = cl.getDeclaredConstructor();
                constructor.setAccessible(true);
                singleton = (Singleton) constructor.newInstance();
            }catch(Exception e){
                e.printStackTrace();
            }
        }
    }
    public static Singleton getSingleton(){
        return SingletonHolder.singleton;
    }
}

public class ProductFactory {
    private static final HashMap<String, Product> prMap = new HashMap<String, Product>();
    public static synchronized Product createProduct(String type) {
        Product product = null;
        if(prMap.containsKey(type))
            product = prMap.get(type);
        else{
            try{
                product = (Product) Class.forName(type).getDeclaredConstructor().newInstance();
                prMap.put(type, product);
            }catch(Exception e){
                e.printStackTrace();
            }
        }
        return product;
    }
}