设计模式-11-享元模式

享元模式：主要用于减少创建对象的数量，以减少内存的占用和提高性能。

享元模式的核心在于享元工厂类，享元工厂类的作用在于提供一个用于存储享元对象的享元池，用户需要对象时，首先从享元池中获取，如果享元池中不存在，则创建一个新的享元对象返回给用户，并在享元池中保存该新增对象。

package com.structuralPattern.enjoy_yuan.edition1;

public abstract class Shape {
public abstract void draw();
}

package com.structuralPattern.enjoy_yuan.edition1;

public class Circle extends Shape{
private String color;
public Circle(String color){
this.color = color;
}

public void draw() {
System.out.println("画了一个" + color +"的圆形");
}

}

package com.structuralPattern.enjoy_yuan.edition1;

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

public class FlyweightFactory{
static Map<String, Shape> shapes = new HashMap<String, Shape>();

public static Shape getShape(String key){
Shape shape = shapes.get(key);
//如果shape==null,表示不存在,则新建,并且保持到共享池中
if(shape == null){
shape = new Circle(key);
shapes.put(key, shape);
}
return shape;
}

public static int getSum(){
return shapes.size();
}
}

package com.structuralPattern.enjoy_yuan.edition1;

public class Client {
public static void main(String[] args) {
Shape shape1 = FlyweightFactory.getShape("红色");
shape1.draw();

Shape shape2 = FlyweightFactory.getShape("灰色");
shape2.draw();

Shape shape3 = FlyweightFactory.getShape("绿色");
shape3.draw();

Shape shape4 = FlyweightFactory.getShape("红色");
shape4.draw();

Shape shape5 = FlyweightFactory.getShape("灰色");
shape5.draw();

Shape shape6 = FlyweightFactory.getShape("灰色");
shape6.draw();

System.out.println("一共绘制了"+FlyweightFactory.getSum()+"中颜色的圆形");
}
}