구조패턴 : Flyweight 패턴

분류 : 구조패턴(Structural Patterns)

정의 :

다른 유사한 객체와 가능한 많은 데이터를 공유함으로써 메모리 사용량을 최소화하는 객체를 flyweight라고 함.

용도 :

메모리 사용량을 줄여서 효율성을 높임.

소스

//Flyweight 객체 인터페이스
public interface CoffeeOrder {
	public void serveCoffee(CoffeeOrderContext context);
}


//ConcreteFlyweight를 생성하는  ConcreteFlyweight 객체
public class CoffeeFlavor implements CoffeeOrder {
	private final String flavor;
	 
    public CoffeeFlavor(String newFlavor) {
        this.flavor = newFlavor;
    }
 
    public String getFlavor() {
        return this.flavor;
    }
 
    public void serveCoffee(CoffeeOrderContext context) {
        System.out.println("Serving Coffee flavor " + flavor + " to table number " + context.getTable());
    }
}

public class CoffeeOrderContext {
	private final int tableNumber;
	 
	public CoffeeOrderContext(int tableNumber) {
		this.tableNumber = tableNumber;
	}
	 
	public int getTable() {
		return this.tableNumber;
	}
}


import java.util.HashMap;
import java.util.Map;

//FlyweightFactory 객체
public class CoffeeFlavorFactory {
	private Map flavors = new HashMap();
	 
    public CoffeeFlavor getCoffeeFlavor(String flavorName) {
        CoffeeFlavor flavor = flavors.get(flavorName);
        if (flavor == null) {
            flavor = new CoffeeFlavor(flavorName);
            flavors.put(flavorName, flavor);
        }
        return flavor;
    }
 
    public int getTotalCoffeeFlavorsMade() {
        return flavors.size();
    }
}

public class TestFlyweight {

	 /** The flavors ordered. */
	   private static CoffeeFlavor[] flavors = new CoffeeFlavor[100];
	   /** The tables for the orders. */
	   private static CoffeeOrderContext[] tables = new CoffeeOrderContext[100];
	   private static int ordersMade = 0;
	   private static CoffeeFlavorFactory flavorFactory;
	 
	   public static void takeOrders(String flavorIn, int table) {
	       flavors[ordersMade] = flavorFactory.getCoffeeFlavor(flavorIn);
	       tables[ordersMade++] = new CoffeeOrderContext(table);
	   }
	 
	   public static void main(String[] args) {
	       flavorFactory = new CoffeeFlavorFactory();
	 
	       takeOrders("Cappuccino", 2);
	       takeOrders("Cappuccino", 2);
	       takeOrders("Frappe", 1);
	       takeOrders("Frappe", 1);
	       takeOrders("Xpresso", 1);
	       takeOrders("Frappe", 897);
	       takeOrders("Cappuccino", 97);
	       takeOrders("Cappuccino", 97);
	       takeOrders("Frappe", 3);
	       takeOrders("Xpresso", 3);
	       takeOrders("Cappuccino", 3);
	       takeOrders("Xpresso", 96);
	       takeOrders("Frappe", 552);
	       takeOrders("Cappuccino", 121);
	       takeOrders("Xpresso", 121);
	 
	       for (int i = 0; i < ordersMade; ++i) {
	           flavors[i].serveCoffee(tables[i]);
	       }
	       System.out.println(" ");
	       System.out.println("total CoffeeFlavor objects made: " +  flavorFactory.getTotalCoffeeFlavorsMade());
	   }

}

참고자료

http://en.wikipedia.org/wiki/Flyweight_pattern#Immutability_.26_Equality

http://www.oodesign.com/flyweight-pattern.html