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Flyweight - a.k.a Cache

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Intent

Flyweight is a structural design pattern that lets you fit more objects into the available amount of RAM by sharing common parts of state between multiple objects instead of keeping all of the data in each object.

Implementation

Applicablity

캐싱

Code Examples


package oodesign.design.structural.flyweight;

public class Flyweight {

    public Flyweight(String data) {
        this.data = data;
    }

    private String data;

    public String getData(){
        return data;
    }

}


package oodesign.design.structural.flyweight;

import java.util.Map;
import java.util.TreeMap;

public class FlyweightFactory {

    Map<Long, Flyweight> pool;

    public FlyweightFactory() {
        this.pool = new TreeMap();
    }

    public Flyweight getFlyweight(Long key){
        Flyweight flyweight = pool.get(key);

        if(flyweight == null){
            flyweight = new Flyweight(String.valueOf(key));
            pool.put(key, flyweight);
            System.out.println("new " + key);
        }else{
            System.out.println("reuse " + key);
        }

        return flyweight;
    }
}


package oodesign.design.structural.flyweight;

public class Main {

    public static void main(String[] args) {
        FlyweightFactory factory = new FlyweightFactory();

        System.out.println("flyweight = " + factory.getFlyweight(1L));
        System.out.println("flyweight = " + factory.getFlyweight(1L));
        System.out.println("flyweight = " + factory.getFlyweight(1L));
        System.out.println("flyweight = " + factory.getFlyweight(2L));

    }
}

실행 결과


new 1
flyweight = oodesign.design.structural.flyweight.Flyweight@3498ed
reuse 1
flyweight = oodesign.design.structural.flyweight.Flyweight@3498ed
reuse 1
flyweight = oodesign.design.structural.flyweight.Flyweight@3498ed
new 2
flyweight = oodesign.design.structural.flyweight.Flyweight@1a407d53

Process finished with exit code 0

Flyweight Pattern

Intent

Implementation

Applicablity

Code Examples