행위패턴 : Strategy 패턴

분류 : 행위패턴(Behavioral Patterns)

정의 :

알고리즘의 동작이 실행시에 결정되는 패턴. 알고리즘의 집합을 정의하고 각각을 캡슐화 한 다음 해당 알고리즘들을 교환가능하게 만듬.

용도 :

입력 데이터의 검증을 수행할때 데이터의 타입에 따라 검증 알고리즘을 선택하도록 함.

소스

/** The classes that implement a concrete strategy should implement this.
* The Context class uses this to call the concrete strategy. */
interface Strategy {
    int execute(int a, int b); 
}


/** Implements the algorithm using the strategy interface */
class Add implements Strategy {
    public int execute(int a, int b) {
        System.out.println("Called Add's execute()");
        return a + b;  // Do an addition with a and b
    }
}


class Subtract implements Strategy {
    public int execute(int a, int b) {
        System.out.println("Called Subtract's execute()");
        return a - b;  // Do a subtraction with a and b
    }
}


class Multiply implements Strategy {
   public int execute(int a, int b) {
       System.out.println("Called Multiply's execute()");
       return a * b;   // Do a multiplication with a and b
   }    
}


/** Configured with a ConcreteStrategy object and maintains a reference to a Strategy object */
class Context {
    private Strategy strategy;
 
    public Context(Strategy strategy) {
        this.strategy = strategy;
    }
 
    public int executeStrategy(int a, int b) {
        return strategy.execute(a, b);
    }
}
 

/** Tests the pattern */
class StrategyExample {
   public static void main(String[] args) {
       Context context;

       // Three contexts following different strategies
       context = new Context(new Add());
       int resultA = context.executeStrategy(3,4);

       context = new Context(new Subtract());
       int resultB = context.executeStrategy(3,4);

       context = new Context(new Multiply());
       int resultC = context.executeStrategy(3,4);

       System.out.println("Result A : " + resultA );
       System.out.println("Result B : " + resultB );
       System.out.println("Result C : " + resultC );
   }
}

참고자료

http://en.wikipedia.org/wiki/Strategy_pattern