Strategy Design Pattern and Factory Method Design Pattern

Question

I start learning Design Patterns. Now I understand a little bit but there are quite a lot of confusions for me. What\'s the difference between Strategy DP and <

Answer 1

Strategies incapsulate different behaviors behind the same interface. You instantiate Strategies with new operator. For example (the same business case as Frederik suggested):

DiscountCalculator calc = new GoogCustomerDiscountCalculator();
Integer discount = calc.calculate();

Factory Method incapsulates instantiation mechanism of some other interface (maybe a Strategy, but maybe something else). For example:

DiscountFactory factory = new DiscountFactory();
DiscountCalculator calc = factory.getDiscountCalculator();
Integer discount = calc.calculate();

Strategy pattern is often used together with Factory Method, while Factory Method is often used for instantiation of other stereotypes, not only Strategies.