{"id":1233,"date":"2022-07-19T21:23:10","date_gmt":"2022-11-22T01:02:27","guid":{"rendered":"https:\/\/www.silicloud.com\/blog\/uncategorized\/example-tutorial-for-the-strategy-design-pattern-in-java\/"},"modified":"2024-03-06T14:05:10","modified_gmt":"2024-03-06T14:05:10","slug":"example-tutorial-for-the-strategy-design-pattern-in-java","status":"publish","type":"post","link":"https:\/\/www.silicloud.com\/blog\/example-tutorial-for-the-strategy-design-pattern-in-java\/","title":{"rendered":"Strategy Design Pattern in Java tutorial"},"content":{"rendered":"

The strategy design pattern falls under the category of behavioral design patterns. It is employed when there are various algorithms available for a particular task, and the client determines the particular implementation to be used at runtime.<\/p>\n

One possible native paraphrase for “Strategy Pattern” could be “Approach Methodology”.<\/h2>\n

The Strategy pattern, also referred to as the Policy Pattern, involves defining numerous algorithms and allowing the client application to pass the desired algorithm as a parameter. An exemplary instance of the strategy pattern is the Collections.sort() method, which takes a Comparator parameter. Depending on the various implementations of the Comparator interface, the objects are sorted in different manners. To illustrate, let’s create a simple Shopping Cart that encompasses two payment strategies: using a Credit Card or using PayPal. Initially, we will establish the interface for our strategy pattern example, which entails paying the specified amount. This interface will be named PaymentStrategy.java<\/a>.<\/p>\n

package com.scdev.design.strategy;\r\n\r\npublic interface PaymentStrategy {\r\n\r\n\tpublic void pay(int amount);\r\n}\r\n<\/code><\/pre>\n
We are now required to develop practical implementations of algorithms for processing payments via credit\/debit cards or PayPal. This will be done through the utilization of the CreditCardStrategy.java file.<\/p>\n
package com.scdev.design.strategy;\r\n\r\npublic class CreditCardStrategy implements PaymentStrategy {\r\n\r\n\tprivate String name;\r\n\tprivate String cardNumber;\r\n\tprivate String cvv;\r\n\tprivate String dateOfExpiry;\r\n\t\r\n\tpublic CreditCardStrategy(String nm, String ccNum, String cvv, String expiryDate){\r\n\t\tthis.name=nm;\r\n\t\tthis.cardNumber=ccNum;\r\n\t\tthis.cvv=cvv;\r\n\t\tthis.dateOfExpiry=expiryDate;\r\n\t}\r\n\t@Override\r\n\tpublic void pay(int amount) {\r\n\t\tSystem.out.println(amount +\" paid with credit\/debit card\");\r\n\t}\r\n\r\n}\r\n<\/code><\/pre>\n
One possible paraphrase could be:<\/p>\n
“Java code file for the PayPal payment strategy.”<\/p>\n
package com.scdev.design.strategy;\r\n\r\npublic class PaypalStrategy implements PaymentStrategy {\r\n\r\n\tprivate String emailId;\r\n\tprivate String password;\r\n\t\r\n\tpublic PaypalStrategy(String email, String pwd){\r\n\t\tthis.emailId=email;\r\n\t\tthis.password=pwd;\r\n\t}\r\n\t\r\n\t@Override\r\n\tpublic void pay(int amount) {\r\n\t\tSystem.out.println(amount + \" paid using Paypal.\");\r\n\t}\r\n\r\n}\r\n<\/code><\/pre>\n
Our algorithms for the strategy pattern example are now prepared. The implementation of the Shopping Cart and payment method will necessitate the input of a Payment strategy in Item.java.<\/p>\n
package com.scdev.design.strategy;\r\n\r\npublic class Item {\r\n\r\n\tprivate String upcCode;\r\n\tprivate int price;\r\n\t\r\n\tpublic Item(String upc, int cost){\r\n\t\tthis.upcCode=upc;\r\n\t\tthis.price=cost;\r\n\t}\r\n\r\n\tpublic String getUpcCode() {\r\n\t\treturn upcCode;\r\n\t}\r\n\r\n\tpublic int getPrice() {\r\n\t\treturn price;\r\n\t}\r\n\t\r\n}\r\n<\/code><\/pre>\n
One possible paraphrase for “ShoppingCart.java” could be “Java code for a shopping cart.”<\/p>\n
package com.scdev.design.strategy;\r\n\r\nimport java.text.DecimalFormat;\r\nimport java.util.ArrayList;\r\nimport java.util.List;\r\n\r\npublic class ShoppingCart {\r\n\r\n\t\/\/List of items\r\n\tList<Item> items;\r\n\t\r\n\tpublic ShoppingCart(){\r\n\t\tthis.items=new ArrayList<Item>();\r\n\t}\r\n\t\r\n\tpublic void addItem(Item item){\r\n\t\tthis.items.add(item);\r\n\t}\r\n\t\r\n\tpublic void removeItem(Item item){\r\n\t\tthis.items.remove(item);\r\n\t}\r\n\t\r\n\tpublic int calculateTotal(){\r\n\t\tint sum = 0;\r\n\t\tfor(Item item : items){\r\n\t\t\tsum += item.getPrice();\r\n\t\t}\r\n\t\treturn sum;\r\n\t}\r\n\t\r\n\tpublic void pay(PaymentStrategy paymentMethod){\r\n\t\tint amount = calculateTotal();\r\n\t\tpaymentMethod.pay(amount);\r\n\t}\r\n}\r\n<\/code><\/pre>\n
Please take note that the payment method of the shopping cart necessitates the payment algorithm as an argument and does not retain it as a variable. Let’s evaluate our strategy pattern example setup using a basic program named ShoppingCartTest.java.<\/p>\n
package com.scdev.design.strategy;\r\n\r\npublic class ShoppingCartTest {\r\n\r\n\tpublic static void main(String[] args) {\r\n\t\tShoppingCart cart = new ShoppingCart();\r\n\t\t\r\n\t\tItem item1 = new Item(\"1234\",10);\r\n\t\tItem item2 = new Item(\"5678\",40);\r\n\t\t\r\n\t\tcart.addItem(item1);\r\n\t\tcart.addItem(item2);\r\n\t\t\r\n\t\t\/\/pay by paypal\r\n\t\tcart.pay(new PaypalStrategy(\"myemail@example.com\", \"mypwd\"));\r\n\t\t\r\n\t\t\/\/pay by credit card\r\n\t\tcart.pay(new CreditCardStrategy(\"Pankaj Kumar\", \"1234567890123456\", \"786\", \"12\/15\"));\r\n\t}\r\n\r\n}\r\n<\/code><\/pre>\n
The program above produces the following result:<\/p>\n
50 paid using Paypal.\r\n50 paid with credit\/debit card\r\n<\/code><\/pre>\n
One possible paraphrase could be: “Class Diagram for the Strategy Design Pattern”<\/h3>\n
Important considerations for the Strategy design pattern.<\/h3>\n