模板方法模式
在软件开发的过程中，如果相同的一段代码复制过两次，就需要对设计产生怀疑。
我们把相同的代码提取出来，提供一个模板，这就叫模板方法模式
看一个例子：
这个例子是悍马车的设计，首先定义几个悍马车的接口
package com.feng.model;
public abstract class HummerModel {
public abstract void start();
public abstract void stop();
public abstract void alarm();
public abstract void enginBoom();
public abstract void run();
}
package com.feng.model;
public class HummerH1Model extends HummerModel{
@Override
public void start() {
// TODO Auto-generated method stub
System.out.println("Hummer H1 start...");
}
@Override
public void stop() {
// TODO Auto-generated method stub
System.out.println("Hummer H1 stop...");
}
@Override
public void alarm() {
// TODO Auto-generated method stub
System.out.println("Hummer H1 alarm...");
}
@Override
public void enginBoom() {
// TODO Auto-generated method stub
System.out.println("Hummer H1 enginBoom...");
}
@Override
public void run() {
// TODO Auto-generated method stub
this.start();
this.enginBoom();
this.alarm();
this.stop();
}
}package com.feng.model;
public class HummerH2Model extends HummerModel{
@Override
public void start() {
// TODO Auto-generated method stub
System.out.println("Hummer H2 start...");
}
@Override
public void stop() {
// TODO Auto-generated method stub
System.out.println("Hummer H2 stop...");
}
@Override
public void alarm() {
// TODO Auto-generated method stub
System.out.println("Hummer H2 alarm...");
}
@Override
public void enginBoom() {
// TODO Auto-generated method stub
System.out.println("Hummer H2 enginBoom...");
}
@Override
public void run() {
// TODO Auto-generated method stub
this.start();
this.enginBoom();
this.alarm();
this.stop();
}
}
Hummer抽象类：
package com.feng.model;
public abstract class HummerModel {
protected abstract void start();
protected abstract void stop();
protected abstract void alarm();
protected abstract void enginBoom();
public void run()
{
this.start();
this.enginBoom();
this.alarm();
this.stop();
}
}
package com.feng.model;
public class HummerH1Model extends HummerModel{
@Override
protected void start() {
// TODO Auto-generated method stub
System.out.println("Hummer H1 start...");
}
@Override
protected void stop() {
// TODO Auto-generated method stub
System.out.println("Hummer H1 stop...");
}
@Override
protected void alarm() {
// TODO Auto-generated method stub
System.out.println("Hummer H1 alarm...");
}
@Override
protected void enginBoom() {
// TODO Auto-generated method stub
System.out.println("Hummer H1 enginBoom...");
}
}package com.feng.model;
public class HummerH2Model extends HummerModel{
@Override
protected void start() {
// TODO Auto-generated method stub
System.out.println("Hummer H2 start...");
}
@Override
protected void stop() {
// TODO Auto-generated method stub
System.out.println("Hummer H2 stop...");
}
@Override
protected void alarm() {
// TODO Auto-generated method stub
System.out.println("Hummer H2 alarm...");
}
@Override
protected void enginBoom() {
// TODO Auto-generated method stub
System.out.println("Hummer H2 enginBoom...");
}
}
package com.feng.model;
public class Test {
public static void main(String[] args)
{
HummerModel hummer = new HummerH1Model();
hummer.run();
}
}
其次，run方法我们还可以定义为final类型，不允许复写。
模板方法模式的优点：
（1）封装不变部分，扩展可变部分
（2）提取公共部分代码，便于维护
（3）行为由父类控制，子类实现
模板方法模式的缺点：
模板方法模式中抽象类定义了部分抽象方法，由子类实现，子类执行结果影响父类的结果。对代码的阅读会带来不便。
模板方法的扩展：
需求总是会变的，如果现在客户要求H1型号的Hummer喇叭想让他想它就响。H2型号的喇叭不要有声音，那怎么改
我们可以在抽象类中加一个方法，这个方法来判断用户要不要车响喇叭。
代码修改如下：
package com.feng.model;
public abstract class HummerModel {
protected abstract void start();
protected abstract void stop();
protected abstract void alarm();
protected abstract void enginBoom();
//钩子方法，默认喇叭是会响的
protected boolean isAlarm()
{
return true;
}
public void run()
{
this.start();
this.enginBoom();
if(isAlarm())
{
this.alarm();
}
this.stop();
}
}
package com.feng.model;
public class HummerH1Model extends HummerModel{
private boolean alarmFlag = true;
@Override
protected void start() {
// TODO Auto-generated method stub
System.out.println("Hummer H1 start...");
}
@Override
protected void stop() {
// TODO Auto-generated method stub
System.out.println("Hummer H1 stop...");
}
@Override
protected void alarm() {
// TODO Auto-generated method stub
System.out.println("Hummer H1 alarm...");
}
@Override
protected void enginBoom() {
// TODO Auto-generated method stub
System.out.println("Hummer H1 enginBoom...");
}
protected boolean isAlarm()
{
return this.alarmFlag;
}
//还要给用户提供一个接口，让用户去设置喇叭应不应该响
public void setAlarm(boolean alarmFlag)
{
this.alarmFlag = alarmFlag;
}
}
package com.feng.model;
public class HummerH2Model extends HummerModel{
@Override
protected void start() {
// TODO Auto-generated method stub
System.out.println("Hummer H2 start...");
}
@Override
protected void stop() {
// TODO Auto-generated method stub
System.out.println("Hummer H2 stop...");
}
@Override
protected void alarm() {
// TODO Auto-generated method stub
System.out.println("Hummer H2 alarm...");
}
@Override
protected void enginBoom() {
// TODO Auto-generated method stub
System.out.println("Hummer H2 enginBoom...");
}
//这个模型的车子永远都不会响喇叭，所以返回false就可以了
protected boolean isAlarm()
{
return false;
}
}
package com.feng.model;
public class Test {
public static void main(String[] args)
{
HummerModel hummer = new HummerH1Model();
hummer.run();
//但是在这想要调用HummerH1Model,必须要构造具体的子类对象才能调用setAlarm()方法
System.out.println("=================");
HummerH1Model h1 = new HummerH1Model();
h1.setAlarm(false);
h1.run();
System.out.println("=================");
hummer = new HummerH2Model();
hummer.run();
}
}