1. 桥接模式

1.1 合成/聚合复用原则

合成/聚合复用原则，尽量使用合成/聚合，尽量不要使用类继承

聚合表示一种弱的拥有关系，体现的是A对象可以包含B对象，但B对象不是A对象的一部分
合成则是一种强的拥有关系，体现了严格的部分和整体的关系，部分和整体的生命周期一样

好处
1）优先使用对象的合成/聚合将有助于你保持每个类被封装，并被集中在单个任务上。这样类和类继承层次都会保持在一个较小的层次上

1.2 桥接模式

桥接模式，将抽象部分与它的实现部分分离，使它们都可以独立地变换

实现指的是抽象类和它的派生类用来实现自己的对象

public abstract class HandsetSoft {
    public abstract void run();
}

public class HandsetGame extends HandsetSoft {
    @Override
    public void run() {
        System.out.println("游戏开始了...");
    }
}

public class HandsetAlbum extends HandsetSoft {
    @Override
    public void run() {
        System.out.println("这是一个相册...");
    }
}

public abstract class HandsetBrand {
    protected HandsetSoft soft;

    public void setSoft(HandsetSoft soft) {
        this.soft = soft;
    }

    public abstract void run();
}

public class HandsetM extends HandsetBrand {
    @Override
    public void run() {
        this.soft.run();
    }
}

public class HandsetClient {
    public static void main(String[] args) {
        HandsetM handsetM= new HandsetM();
        handsetM.setSoft(new HandsetGame());
        handsetM.run();
    }
}

Handset桥接模式

桥接模式

2. 命令模式

命令模式，将一个请求封装为一个对象，从而使你可用不同的请求对客户进行参数化，对请求排队或记录请求日志，以及支持可撤销的操作

命令模式

public abstract class Command {
    Receiver receiver;

    public Command(Receiver receiver) {
        this.receiver = receiver;
    }
    public abstract void executeCommand();
}

public class BakeCommand extends Command {
    public BakeCommand(Receiver receiver) {
        super(receiver);
    }

    @Override
    public void executeCommand() {
        receiver.Action();
    }
}

import java.util.ArrayList;

public class Waiter {
    ArrayList<Command> commandArrayList = new ArrayList<>();

    public void cancelCommand(Command command) {
        commandArrayList.remove(command);
    }

    public void addCommand(Command command) {
        commandArrayList.add(command);
    }

    public void submitCommand() {
        for(Command command: commandArrayList) {
            command.executeCommand();
        }
    }
}

public class Receiver {
    public void Action() {
        System.out.println("蛋糕做好了！");
    }
}

public class CommandClient {
    public static void main(String[] args) {
        //开店前的准备
        Waiter girl = new Waiter();
        Receiver baker = new Receiver();
        BakeCommand bakeCommand = new BakeCommand(baker);

        // 开始点餐
        girl.addCommand(bakeCommand);
        girl.submitCommand();
    }
}

能比较容易地设计一个命令队列
将命令放入日志
允许接收方决定是否接受请求
容易实现决定的撤销和重做
增加新命令很简单
只有真正需要如撤销/恢复操作等功能时，把原来的代码重构为命令模式才有意义

3. 职责链模式

职责链模式，使得多个对象都有机会处理请求，从而避免请求的发送者和接收者之间的耦合关系。将这个对象连成一条链，并沿着这条链传递该请求，直到有一个对象处理它为止

public abstract class Handler {
    public Handler successor;

    public void setSuccessor (Handler successor) {
        this.successor = successor;
    }

    public abstract void handleRequest(int request);
}

public class ConcreteHandler extends Handler {

    @Override
    public void handleRequest(int request) {
        if( request < 10) {
            System.out.println("ConcreteHandler have handled request " + request);
        }
        else if (successor != null){
            successor.handleRequest(request);
        }
    }
}

public class ConcreteHandler2 extends Handler {
    @Override
    public void handleRequest(int request) {
        if(request > 10 && request < 100) {
            System.out.println("ConcreteHandler2 have handled request " + request);
        } else {
            System.out.println("Nobody  can handle");
        }
    }
}

public class HandlerClient {
    public static void main(String[] args) {
        ConcreteHandler concreteHandler = new ConcreteHandler();
        ConcreteHandler2 concreteHandler2 = new ConcreteHandler2();
        concreteHandler.setSuccessor(concreteHandler2);

        concreteHandler.handleRequest(5);
        concreteHandler.handleRequest(40);
    }

}