Java设计模式（五）外观模式 桥梁模式

（九）外观模式

外观模式为子系统提供一个接口，便于使用。解决了类与类之间关系的，外观模式将类之间的关系放在一个 Facade 类中，降低了类类之间的耦合度，该模式不涉及接口。

class CPU {public void startup(){System.out.println("cpu start");}public void shutdown(){System.out.println("cpu stop");}}class Memory {public void startup(){System.out.println("Memory start");}public void shutdown(){System.out.println("Memory stop");}}class Disk {public void startup(){System.out.println("Disk start");}public void shutdown(){System.out.println("Disk stop");}}class Computer{private CPU cpu;private Memory memory;private Disk disk;public Computer(){cpu = new CPU();memory = new Memory();disk = new Disk();} public void startup(){          System.out.println("start the computer!");          cpu.startup();          memory.startup();          disk.startup();          System.out.println("start computer finished!");      }            public void shutdown(){          System.out.println("begin to close the computer!");          cpu.shutdown();          memory.shutdown();          disk.shutdown();          System.out.println("computer closed!");      }  }public class Facade {public static void main(String[] args){Computer computer = new Computer();computer.startup(); computer.shutdown();}}

外观模式将表现层与逻辑层隔离，封装底层的复杂处理，为用户提供简单的接口。
（十）桥梁模式 Bridge

桥梁模式就是吧事物和具体的实现分开，将抽象与抽象方法的实现相互分离来实现解耦，以便两者能够相互独立的变化。

interface Fruit{public void method();}class Apple implements Fruit{public void method(){System.out.println("Apple");}}class Pear implements Fruit{public void method(){System.out.println("Pear");}}abstract class Bridge{private Fruit fruit;public void method(){fruit.method();}public Fruit getFruit(){return fruit;}public void setFruit(Fruit fruit){this.fruit = fruit;}}class MyBridge extends Bridge{public void method(){getFruit().method();}}public class BridgeTest {public static void main(String[] args){Bridge bridge = new MyBridge();Fruit apple = new Apple();bridge.setFruit(apple);bridge.method();Fruit pear = new Pear();bridge.setFruit(pear);bridge.method();}}