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Bridge Pattern in Design Pattern

桥接模式

Overview

桥接(Bridge)是用于把抽象化与实现化解耦,使得二者可以独立变化。

这种类型的设计模式属于结构型模式,它通过提供抽象化和实现化之间的桥接结构,来实现二者的解耦。

这种模式涉及到一个作为桥接的接口,使得实体类的功能独立于接口实现类。

这两种类型的类可被结构化改变而互不影响。

主要解决

在有多种可能会变化的情况下,用继承会造成类爆炸问题,扩展起来不灵活

何时使用

实现系统可能有多个角度分类,每一种角度都可能变化

应用实例

  • 墙上的开关,可以看到的开关是抽象的,不用管里面具体怎么实现的

优点

  • 抽象和实现的分离
  • 优秀的扩展能力
  • 实现细节对客户透明

实现

Bridge Pattern

DrawApi

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package individual.cy.learn.pattern.structural.bridge;

/**
* @author mystic
*/
public interface DrawApi {
/**
* To draw a circle
* @param radius radius
* @param x Abscissa, X-axis
* @param y ordinate, Y-axis
*/
void drawCircle(int radius, int x, int y);
}

RedCircle

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package individual.cy.learn.pattern.structural.bridge;

/**
* @author mystic
*/
public class RedCircle implements DrawApi {
@Override
public void drawCircle(int radius, int x, int y) {
System.out.println("[Draw a red circle] radius = " + radius + ", x = " + x + ", y = " + y);
}
}

PurpleCircle

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package individual.cy.learn.pattern.structural.bridge;

/**
* @author mystic
*/
public class PurpleCircle implements DrawApi {
@Override
public void drawCircle(int radius, int x, int y) {
System.out.println("[Draw a purple circle] radius = " + radius + ", x = " + x + ", y = " + y);
}
}

BaseShape

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package individual.cy.learn.pattern.structural.bridge;

/**
* @author mystic
*/
public abstract class BaseShape {
protected DrawApi drawApi;

protected BaseShape(DrawApi drawApi) {
this.drawApi = drawApi;
}

/**
* To draw a geometric shape
*/
public abstract void draw();
}

Circle

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package individual.cy.learn.pattern.structural.bridge;

/**
* @author mystic
*/
public class Circle extends BaseShape {
private final int x;
private final int y;
private final int radius;

public Circle(DrawApi drawApi, int x, int y, int radius) {
super(drawApi);
this.x = x;
this.y = y;
this.radius = radius;
}

@Override
public void draw() {
drawApi.drawCircle(radius, x, y);
}
}

Tester

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package individual.cy.learn.pattern.structural.bridge;

/**
* @author mystic
*/
public class BridgePatternTester {
public static void main(String[] args) {
BaseShape redCircle = new Circle(new RedCircle(), 0, 0, 3);
BaseShape purpleCircle = new Circle(new PurpleCircle(), 0, 6, 3);

redCircle.draw();
purpleCircle.draw();
}
}

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[Draw a red circle] radius = 3, x = 0, y = 0
[Draw a purple circle] radius = 3, x = 0, y = 6