出库管理|零件设计中的状态模式学习心得与应用分析

篇首语：本文由编程笔记#小编为大家整理，主要介绍了设计模式学习笔记之状态模式相关的知识，希望对你有一定的参考价值。

什么是状态模式呢&＃xff1f;

允许一个对象在其内部状态改变时改变它的行为。对象看起来似乎修改了它的类。。。是不是听起来显示在内部进行零件调换的感觉&＃xff0c;其实是有点类似这种想法的&＃xff0c;只不过调换的零件就是封装好的状态。

让我们来举个例子

在我还上学的时候&＃xff0c;寝室楼下有一台这样的自动贩售机&＃xff0c;专门卖饮料。每天晚上寝室关门之后口渴了&＃xff0c;在这里面买点饮料喝喝还是很方便的。

下面用程序来模拟一下这个售货机&＃xff1a;

可乐售货机类&＃xff1a;

/**
*
* 可乐自动贩售机类
* &＃64;author birdlove1987
*
*/
public class VendingMachine

//售空
final static int SoldOutState &＃61; 0;

//在售
final static int OnReadyState &＃61; 1;

//有币
final static int HasCoin &＃61; 2;

//出货
final static int SoldState &＃61; 3;
//售货机状态
private int state &＃61; SoldOutState;

//机内可乐数量
private int count &＃61; 0;
//构造函数&＃xff0c;初始化自动贩售机
public VendingMachine(int count)

this.count &＃61; count;
if (count > 0)
state &＃61; OnReadyState;


//向贩售机投币函数
public void insertCoin()

switch (state)

case SoldOutState:
System.out.println("请不要投币了&＃xff0c;售货机里已经没有可乐了&＃xff01;");
break;
case OnReadyState:
state &＃61; HasCoin;
System.out.println("投币成功&＃xff0c;请按出货按钮&＃xff01;");
break;
case HasCoin:
System.out.println("售货机里以及有硬币了&＃xff0c;请勿重复投币&＃xff01;");
break;
case SoldState:
System.out.println("正在出货请勿投币&＃xff01;");
break;


//贩售机退币函数
public void returnCoin()

switch (state)

case SoldOutState:
System.out.println("您还没有投币&＃xff01;");
break;
case OnReadyState:
System.out.println("您还没有投币&＃xff01;");
break;
case HasCoin:
System.out.println("请在退币口收好您的硬币");
state &＃61; OnReadyState;
break;
case SoldState:
System.out.println("可乐已售出&＃xff0c;不能退币");
break;


//按出可乐按钮函数
public void pressButton()

switch (state)

case SoldOutState:
System.out.println("对不起&＃xff0c;可乐已售空&＃xff01;");
break;
case OnReadyState:
System.out.println("请您先投币&＃xff01;");
break;
case HasCoin:
System.out.println("请稍等&＃xff0c;出可乐中&＃xff01;");
state &＃61; SoldState;
appearCola();
break;
case SoldState:
System.out.println("可乐已出&＃xff0c;如想再次购买请再次投币&＃xff01;");
break;


//售货机出可乐函数
private void appearCola()

count &＃61; count - 1;
System.out.println("出货口&＃xff0c;滚出了一瓶可乐&＃xff01;");
if (count > 0)

state &＃61; OnReadyState;

else

System.out.println("对不起&＃xff0c;可乐已经售空了&＃xff0c;请勿在投币&＃xff01;");
state &＃61; SoldOutState;


//打印目前售货机的状态
public void printState()

switch (state)

case SoldOutState:
System.out.println("&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;售空&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;");
break;
case OnReadyState:
System.out.println("&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;售卖中&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;");
break;
case HasCoin:
System.out.println("&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;已投币&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;");
break;
case SoldState:
System.out.println("&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;出货中&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;");
break;




测试类

/**
* 测试类
* &＃64;author birdlove1987
*
*/
public class MainTest
public static void main(String[] args)

//创建售货机实例&＃xff0c;并且只放入一瓶可乐
VendingMachine mVendingMachine&＃61;new VendingMachine(1);


//打印售货机状态
mVendingMachine.printState();

//投币
mVendingMachine.insertCoin();

//打印售货机状态
mVendingMachine.printState();

//按出货按钮
mVendingMachine.pressButton();


//打印售货机状态
mVendingMachine.printState();

//投币
mVendingMachine.insertCoin();

//打印售货机状态
mVendingMachine.printState();

//按出货按钮
mVendingMachine.pressButton();

//打印售货机状态
mVendingMachine.printState();



嗯&＃xff01;模拟成功了&＃xff01;好像感觉还不错呢&＃xff01;不过买了一段时间&＃xff0c;你可能发现&＃xff0c;如果不搞一些促销活动&＃xff0c;更本就搞不过那些有促销的商家&＃xff01;

所以自动售货机也要搞一个“再来一瓶”的活动啊&＃xff01;

但是&＃xff01;&＃xff01;&＃xff01;如果现在直接在自动售货机的类上去直接修改&＃xff0c;就违背了软件设计里的“开-闭原则”了&＃xff0c;破坏了我们已经闭合的类。所以现在看来&＃xff0c;这种设计并不好。。

下面就轮到状态设计模式登场啦&＃xff0c;我们从新构建类&＃xff0c;这次以状态为类&＃xff0c;来构建。

首先定义一下状态接口

/***
* 状态接口
* &＃64;author birdlove1987
*
*/
public interface State

//投币函数
public void insertCoin();

//退币函数
public void returnCoin();

//按出可乐按钮函数
public void pressButton();

//出可乐函数
public void appearCola();

//打印状态函数
public void printState();



/***
* 在售状态类
* &＃64;author birdlove1987
*
*/
public class OnReadyState implements State

//贩售机引用
private VendingMachine mVendingMachine;

//构造函数初始化
public OnReadyState(VendingMachine mVendingMachine)

this.mVendingMachine&＃61;mVendingMachine;


&＃64;Override
public void insertCoin()

// TODO Auto-generated method stub
System.out.println("投币成功&＃xff0c;请按出货按钮&＃xff01;");
mVendingMachine.setState(mVendingMachine.mHasCoin);

&＃64;Override
public void returnCoin()

// TODO Auto-generated method stub
System.out.println("您还没有投币&＃xff01;");


&＃64;Override
public void pressButton()

// TODO Auto-generated method stub
System.out.println("请您先投币&＃xff01;");


&＃64;Override
public void appearCola()

// TODO Auto-generated method stub

&＃64;Override
public void printState()

// TODO Auto-generated method stub
System.out.println("&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;售卖中&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;");

/***
* 售空状态类
* &＃64;author birdlove1987
*
*/
public class SoldOutState implements State
private VendingMachine mVendingMachine;
public SoldOutState(VendingMachine mCandyMachine)

this.mVendingMachine&＃61;mVendingMachine;

&＃64;Override
public void insertCoin()

// TODO Auto-generated method stub
System.out.println("请不要投币了&＃xff0c;售货机里已经没有可乐了&＃xff01;");


&＃64;Override
public void returnCoin()

// TODO Auto-generated method stub
System.out
.println("您还没有投币&＃xff01;");

&＃64;Override
public void pressButton()

// TODO Auto-generated method stub
System.out.println("对不起&＃xff0c;可乐已售空&＃xff01;");


&＃64;Override
public void appearCola()

// TODO Auto-generated method stub

&＃64;Override
public void printState()
// TODO Auto-generated method stub
System.out.println("&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;售空&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;");



/***
* 已投币状态类
* &＃64;author birdlove1987
*
*/
public class HasCoin implements State

private VendingMachine mVendingMachine;
public HasCoin(VendingMachine mVendingMachine)

this.mVendingMachine &＃61; mVendingMachine;

&＃64;Override
public void insertCoin()

// TODO Auto-generated method stub
System.out.println("售货机里以及有硬币了&＃xff0c;请勿重复投币&＃xff01;");

&＃64;Override
public void returnCoin()

// TODO Auto-generated method stub
System.out.println("请在退币口收好您的硬币");
mVendingMachine.setState(mVendingMachine.mOnReadyState);

&＃64;Override
public void pressButton()

// TODO Auto-generated method stub
System.out.println("请稍等&＃xff0c;出可乐中&＃xff01;");

//创建随机中奖概率
Random anotherOne &＃61; new Random();

//20%的机会再来一瓶
int luck &＃61; anotherOne.nextInt(5);
if(luck&＃61;&＃61;0)

mVendingMachine.setState(mVendingMachine.mOneMoreCola);
else

mVendingMachine.setState(mVendingMachine.mSoldState);


&＃64;Override
public void appearCola()


&＃64;Override
public void printState()

// TODO Auto-generated method stub
System.out.println("&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;已投币&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;");

/**
* 出可乐状态类
* &＃64;author birdlove1987
*
*/
public class SoldState implements State
private VendingMachine mVendingMachine;
public SoldState(VendingMachine mVendingMachine)

this.mVendingMachine&＃61;mVendingMachine;

&＃64;Override
public void insertCoin()

// TODO Auto-generated method stub
System.out.println("正在出货请勿投币&＃xff01;");

&＃64;Override
public void returnCoin()

// TODO Auto-generated method stub
System.out.println("可乐已售出&＃xff0c;不能退币");


&＃64;Override
public void pressButton()

// TODO Auto-generated method stub
System.out
.println("可乐已出&＃xff0c;如想再次购买请再次投币&＃xff01;");

&＃64;Override
public void appearCola()

// TODO Auto-generated method stub

mVendingMachine.appearCola();
if (mVendingMachine.getCount() > 0)

mVendingMachine.setState(mVendingMachine.mOnReadyState);

else

System.out.println("对不起&＃xff0c;可乐已经售空了&＃xff0c;请勿在投币&＃xff01;");
mVendingMachine.setState(mVendingMachine.mSoldOutState);



&＃64;Override
public void printState()

// TODO Auto-generated method stub
System.out.println("&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;出货中&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;");


/***
* 再来一瓶类
* &＃64;author birdlove1987
*
*/
public class OneMoreCola implements State
private VendingMachine mVendingMachine;
public OneMoreCola(VendingMachine mVendingMachine)

this.mVendingMachine &＃61; mVendingMachine;

&＃64;Override
public void insertCoin()

// TODO Auto-generated method stub
System.out.println("正在出货请勿投币&＃xff01;");

&＃64;Override
public void returnCoin()

// TODO Auto-generated method stub
System.out.println("可乐已售出&＃xff0c;不能退币");

&＃64;Override
public void pressButton()

// TODO Auto-generated method stub
System.out.println("请稍等&＃xff0c;出可乐中&＃xff01;");

&＃64;Override
public void appearCola()

// TODO Auto-generated method stub

mVendingMachine.appearCola();
if (mVendingMachine.getCount() &＃61;&＃61; 0)

mVendingMachine.setState(mVendingMachine.mSoldOutState);

else

System.out.println("恭喜你获得了再来一瓶&＃xff0c;马上为您再出一瓶可乐");
mVendingMachine.appearCola();
if (mVendingMachine.getCount() > 0)

mVendingMachine.setState(mVendingMachine.mOnReadyState);

else

System.out.println("对不起&＃xff0c;可乐已经售空了&＃xff0c;请勿在投币&＃xff01;");
mVendingMachine.setState(mVendingMachine.mSoldOutState);



&＃64;Override
public void printState()

// TODO Auto-generated method stub
System.out.println("&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;再来一瓶&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;");




/**
* 自动售货机类
* &＃64;author birdlove1987
*
*/
public class VendingMachine
//状态类引用
State mSoldOutState;
State mOnReadyState;
State mHasCoin;
State mSoldState;
State mOneMoreCola;

//目前状态
private State state;

//可乐计数器
private int count &＃61; 0;
//构造函数
public VendingMachine(int count)

this.count &＃61; count;
mSoldOutState &＃61; new SoldOutState(this);
mOnReadyState &＃61; new OnReadyState(this);
mHasCoin &＃61; new HasCoin(this);
mSoldState &＃61; new SoldState(this);
mOneMoreCola &＃61; new OneMoreCola(this);
if (count > 0)

state &＃61; mOnReadyState;

else

state &＃61; mSoldOutState;


//设置状态函数
public void setState(State state)

this.state &＃61; state;

//投币函数
public void insertCoin()

state.insertCoin();


//退币函数
public void returnCoin()

state.returnCoin();


//按出可乐按钮函数
public void pressButton()

state.pressButton();
state.appearCola();

//出可乐函数
void appearCola()

// TODO Auto-generated method stub
if (count > 0)

count &＃61; count - 1;
System.out.println("出货口&＃xff0c;滚出了一瓶可乐&＃xff01;");


//可乐计数函数
public int getCount()

return count;


//打印状态函数
public void printState()

state.printState();



/**
* 测试类
* &＃64;author birdlove1987
*
*/
public class MainTest
public static void main(String[] args)


//实例化自动贩售机对象
VendingMachine mVendingMachine &＃61; new VendingMachine(10);

//打印状态
mVendingMachine.printState();
//投币
mVendingMachine.insertCoin();

//打印状态
mVendingMachine.printState();
//按出可乐按钮
mVendingMachine.pressButton();
//打印状态
mVendingMachine.printState();
//投币
mVendingMachine.insertCoin();

//打印状态
mVendingMachine.printState();
//按出可乐按钮
mVendingMachine.pressButton();
//打印状态
mVendingMachine.printState();



中了一次。。。好吧&＃xff0c;我来作弊一下。。调到100%

哈哈哈&＃xff01;

状态模式的优点
    1.状态模式将与特定状态相关的行为局部化&＃xff0c;并且将不同状态的行为分割开来。
    2.将与状态有关的行为封装到一个类中&＃xff0c;方便地增加新的状态&＃xff0c;只需改变对象状态即可改变对象的行为。 
    3.提供代码复用性&＃xff0c;降低了程序的某些耦合性。   
     
状态模式的缺点
    1.有时候状态类会很多&＃xff0c;而且逻辑复杂。

状态模式适用场景
    1、对象的行为依赖于它的状态&＃xff0c;并且其行为依据它的状态改变而改变。 
    2、代码中包含大量与对象状态有关的条件语句。