Design Patterns: Template Method

Template Method defines a framework for operation of the algorithm, some steps to subclasses delay. Subclasses may not change such a configuration algorithm to certain steps of the algorithm to redefine

The main role of a template method

Template Method pattern using Java inheritance mechanism, which, AbstractClass called the abstract template , its methods are divided into two categories:

• The basic methods: by subclass to achieve, and is called template method
• Template Methods: The basic scheduling method implemented, in fixed logic

ConcreteClass1 and belong ConcreteClass2 specific template , the basic method as defined in the parent class implementation

2, to achieve a template method

//抽象模板类
public abstract class AbstractClass {
    //基本方法
    protected abstract void doSomething();

    //基本方法
    protected abstract void doAnything();

    public void templateMethod() {
        //调用基本方法，完成相关逻辑
        this.doAnything();
        this.doSomething();
    }
}

//具体模板类
public class ConcreteClass1 extends AbstractClass {
    @Override
    protected void doSomething() {
        //业务逻辑
    }

    @Override
    protected void doAnything() {
        //业务逻辑
    }
}

//具体模板类
public class ConcreteClass2 extends AbstractClass {
    @Override
    protected void doSomething() {
        //业务逻辑
    }

    @Override
    protected void doAnything() {
        //业务逻辑
    }
}

public class Client {
    public static void main(String[] args) {
        AbstractClass class1 = new ConcreteClass1();
        AbstractClass class2 = new ConcreteClass2();
        //调用模板方法
        class1.templateMethod();
        class2.templateMethod();
    }
}

3, extended template method

Business logic is as follows: H1 Hummer models can control whether it loud horn

//抽象模板类
public abstract class HummerMode {
    protected abstract void start();

    protected abstract void stop();

    protected abstract void alarm();

    protected abstract void engineBoom();

    final public void run() {
        //发动汽车
        this.start();
        //引擎开始轰鸣
        this.engineBoom();
        //汽车喇叭响
        if (isAlarm()) {
            this.alarm();
        }
        //到达目的地停车
        this.stop();
    }

    //钩子方法，默认喇叭是会响的
    protected boolean isAlarm() {
        return true;
    }
}

//具体模板类
public class HummerH1 extends HummerMode {
    private boolean alarmFlag = true;//要响喇叭

    public void setAlarm(boolean isAlarm) {
        this.alarmFlag = isAlarm;
    }

  	//重写钩子方法，通过子类方法返回值决定公共部分的执行结果
    @Override
    protected boolean isAlarm() {
        return this.alarmFlag;
    }

    @Override
    protected void start() {
        System.out.println("悍马H1发送...");
    }

    @Override
    protected void stop() {
        System.out.println("悍马H1停车...");
    }

    @Override
    protected void alarm() {
        System.out.println("悍马H1鸣笛...");
    }

    @Override
    protected void engineBoom() {
        System.out.println("悍马H1引擎发动...");
    }
}

public class Client {
    public static void main(String[] args) throws IOException {
        System.out.println("H1型号悍马");
        System.out.println("H1型号悍马是否需要喇叭声响？ 0-不需要 1-需要");
        String type = new BufferedReader(new InputStreamReader(System.in)).readLine();
        HummerH1 h1 = new HummerH1();
        if (type.equals("0")) h1.setAlarm(false);
        h1.run();
    }
}

0 input operation result as follows:

H1型号悍马
H1型号悍马是否需要喇叭声响？ 0-不需要 1-需要
0
悍马H1发送...
悍马H1引擎发动...
悍马H1停车...

The result of running the input 1 as follows:

H1型号悍马
H1型号悍马是否需要喇叭声响？ 0-不需要 1-需要
1
悍马H1发送...
悍马H1引擎发动...
悍马H1鸣笛...
悍马H1停车...