Java设计模式--享元模式
2018-04-18 本文已影响0人
留给时光吧
享元模式主要是利用对对象的重复使用来减低内存的使用,主要思想是建立一个类似对象池的东西,对池内对象实现充分复用。简单实现:
抽象接口
public interface Shape {
void draw();
}
具体实现
public class Circle implements Shape{
private String color;
private int x,y,r;
public Circle(String color){
this.color = color;
}
public void setXYR(int x,int y,int r){
this.x = x;
this.y = y;
this.r = r;
}
@Override
public void draw() {
System.out.println("draw circle: x = " + x + " , y = " + y + " , r = " + r + " , color = " + color);
}
}
对象池管理类,对外提供对象
public class ShapeFactory {
private static final HashMap<String,Shape> map = new HashMap<>();
public static Shape getCircle(String color){
Circle circle = (Circle) map.get(color);
if(circle == null){
circle = new Circle(color);
map.put(color,circle);
System.out.println("create circle : " + color);
}
return circle;
}
}
测试类
public class test {
private static final String colors[] =
{ "Red", "Green", "Blue"};
public static void main(String[] args) {
for(int i=0; i < 10; ++i) {
Circle circle =
(Circle) ShapeFactory.getCircle(getRandomColor());
circle.setXYR(getRandomX(),getRandomY(),10);
circle.draw();
}
}
private static String getRandomColor() {
return colors[(int)(Math.random()*colors.length)];
}
private static int getRandomX() {
return (int)(Math.random()*100 );
}
private static int getRandomY() {
return (int)(Math.random()*100);
}
}
结果:
create circle : Red
draw circle: x = 58 , y = 99 , r = 10 , color = Red
create circle : Blue
draw circle: x = 58 , y = 24 , r = 10 , color = Blue
create circle : Green
draw circle: x = 82 , y = 45 , r = 10 , color = Green
draw circle: x = 99 , y = 61 , r = 10 , color = Green
draw circle: x = 36 , y = 51 , r = 10 , color = Blue
draw circle: x = 41 , y = 71 , r = 10 , color = Green
draw circle: x = 2 , y = 3 , r = 10 , color = Green
draw circle: x = 35 , y = 74 , r = 10 , color = Green
draw circle: x = 25 , y = 74 , r = 10 , color = Green
draw circle: x = 0 , y = 29 , r = 10 , color = Green
可以发现,虽然我们调用了10次draw,每次circle对象的属性都不同,但是我们只实例化了3个对象,这样在打了频繁的调用某些类似对象时,能极大的减少资源消耗