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strategy pattern

admin 11月 14, 2020 0

There are common situations when classes differ only in their behavior. For this cases is a good idea to isolate the algorithms in separate classes in order to have the ability to select different algorithms at runtime.

Intent

Define a family of algorithms, encapsulate each one, and make them interchangeable. Strategy lets the algorithm vary independently from the clients that use it.
Capture the abstraction in an interface, bury implementation details in derived classes.

Implementation

We are going to create a Strategy interface defining an action and concrete strategy classes implementing the Strategy interface. Context is a class which uses a Strategy.

public interface  {
   public int doOperation(int num1, int num2);
}

// OperationAdd.java
public class OperationAdd implements {
   
   public int doOperation(int num1, int num2) {
      return num1 + num2;
   }
}

// OperationSubstract.java
public class OperationSubstract implements {
   
   public int doOperation(int num1, int num2) {
      return num1 - num2;
   }
}

// Context.java
public class Context {
   private Strategy strategy;
   public Context(Strategy strategy){
      this.strategy = strategy;
   }
   public int executeStrategy(int num1, int num2){
      return strategy.doOperation(num1, num2);
   }
}

// StrategyPatternDemo.java
public class StrategyPatternDemo {
   public static void main(String[] args) {
      Context context = new Context(new OperationAdd());
      System.out.println("10 + 5 = " + context.executeStrategy(10, 5));
      context = new Context(new OperationSubstract());
      System.out.println("10 - 5 = " + context.executeStrategy(10, 5));
   }
}

Reference