一箫攀、浩言

人靜而后安，安而能后定幼衰，定而能后慧靴跛，慧而能后悟，悟而能后得渡嚣。

二梢睛、背景

開年，看了看最近網(wǎng)上傳的《阿里巴巴Java開發(fā)規(guī)范》,然后看到了如下一部分识椰。

Paste_Image.png

這里說如果if else if else超過了三層就需要使用狀態(tài)設(shè)計模式扬绪。碰巧年前我寫了一個訂單狀態(tài)轉(zhuǎn)換的代碼，我沒有使用if else if else的形式裤唠，我使用了case，如果改為if等 就是if else if else形式了毅整。

code.png

所以我就在思考他嚷，這段代碼是否可以改為所說的狀態(tài)設(shè)計模式了?

三、狀態(tài)設(shè)計模式

3.1狀態(tài)模式定義：
狀態(tài)模式是屬于行為模式的范疇渗钉，即是對象在內(nèi)部狀態(tài)改變時改變它的行為航瞭，對象看起來好像修改了它的類诫硕。
下圖是截取《Head First 設(shè)計模式》中的圖片

Paste_Image.png

package com.mouse.design.state;
/**
 * Created by wuhao on 2017/2/7.
 */
public interface State {

    public void insertQuarter();

    public void ejectQuarter();

    public void turnCrank();

    public void dispense();
}

package com.mouse.design.state;
/**
 * Created by wuhao on 2017/2/7.
 */
public class GumballMachine {
    State hasQuarterState;
    State noQuarterState;
    State soldOutState;
    State soldState;
    State winnerState;
    State state = soldOutState;
    int count = 0;
    public GumballMachine(int numberCount) {
        this.count = numberCount;
        hasQuarterState = new HasQuarterState(this);
        noQuarterState = new NoQuarterState(this);
        soldOutState = new SoldOutState(this);
        soldState = new SoldState(this);
        winnerState = new WinnerState(this);
        if (numberCount > 0) {
            state = noQuarterState;
        }
    }
    /**
     * 投幣
     */
    public void insertQuarter() {
        state.insertQuarter();
    }
    /**
     * 退還硬幣
     */
    public void ejectQuarter() {
        state.ejectQuarter();
    }
    /**
     * 轉(zhuǎn)動轉(zhuǎn)軸
     */
    public void turnCrank() {
        state.turnCrank();
        state.dispense();
    }
    void setState(State state) {
        this.state = state;
    }
    /**
     * 釋放糖果并且糖果數(shù)減1;
     */
    void releaseBall() {
        System.out.println("a gumball comes rolling  out the slot");
        if (count != 0) {
            count = count - 1;
        }
    }
    public State getHasQuarterState() {
        return hasQuarterState;
    }
    public void setHasQuarterState(State hasQuarterState) {
        this.hasQuarterState = hasQuarterState;
    }
    public State getNoQuarterState() {
        return noQuarterState;
    }
    public void setNoQuarterState(State noQuarterState) {
        this.noQuarterState = noQuarterState;
    }
    public State getSoldOutState() {
        return soldOutState;
    }
    public void setSoldOutState(State soldOutState) {
        this.soldOutState = soldOutState;
    }
    public State getSoldState() {
        return soldState;
    }
    public void setSoldState(State soldState) {
        this.soldState = soldState;
    }
    public State getWinnerState() {
        return winnerState;
    }
    public void setWinnerState(State winnerState) {
        this.winnerState = winnerState;
    }
    public State getState() {
        return state;
    }
    public int getCount() {
        return count;
    }
    public void setCount(int count) {
        this.count = count;
    }
}

HasQuarterState類

package com.mouse.design.state;
import java.util.Random;
/**
 * Created by wuhao on 2017/2/7.
 */
public class HasQuarterState implements State {

    GumballMachine gumballMachine;

    public HasQuarterState(GumballMachine gumballMachine) {
        this.gumballMachine = gumballMachine;
    }

    @Override
    public void insertQuarter() {
        System.out.println("你不能重復(fù)投幣");
    }

    @Override
    public void ejectQuarter() {
        System.out.println("退還投入的硬幣！１醭埂藕届！");
        gumballMachine.setState(gumballMachine.getNoQuarterState());
    }

    @Override
    public void turnCrank() {
        System.out.println("you turn...");
        int win = new Random().nextInt(10);
        System.out.println("win--->"+win);
        if( (0 == win) && gumballMachine.getCount() > 0  ){
            gumballMachine.setState(gumballMachine.getWinnerState());
        }else{
            gumballMachine.setState(gumballMachine.getSoldState());
        }
    }
    @Override
    public void dispense() {
        System.out.println("No gumball dispensed...");
    }
}

client.java類

package com.mouse.design.state;
/**
 * Created by wuhao on 2017/2/7.
 */
public class Client {
    public static void main(String[] args) {
        GumballMachine  gumballMachine = new GumballMachine(5);
        System.out.println("---------1--------");
        gumballMachine.insertQuarter();
        gumballMachine.turnCrank();

        System.out.println("--------2-----");
        gumballMachine.insertQuarter();
        gumballMachine.turnCrank();

        System.out.println("------3-------");
        gumballMachine.insertQuarter();
        gumballMachine.turnCrank();

        System.out.println("------4-------");
        gumballMachine.insertQuarter();
        gumballMachine.turnCrank();

        System.out.println("------5-------");
        gumballMachine.insertQuarter();
        gumballMachine.turnCrank();

        System.out.println("------6-------");
        gumballMachine.insertQuarter();
        gumballMachine.turnCrank();
    }
}

3.3 代碼
代碼已經(jīng)上傳到github上了，之前一直用bitbucket亭饵，不過現(xiàn)在把一些代碼弄到github上休偶。
https://github.com/MahoneWu/mouse-java-git.git

四：思考

最近看那個規(guī)范，覺得對于我來說還是有很大很大幫助的辜羊，其中的一些東西注意項(xiàng)踏兜，有說到需要注意的設(shè)計模式，比如"模板設(shè)計模式"八秃，這篇寫的"狀態(tài)設(shè)計模式"碱妆，其實(shí)設(shè)計模式在思維上是很特別的，寫法也是昔驱。所以狀態(tài)設(shè)計模式一般用于"狀態(tài)的變化并且業(yè)務(wù)復(fù)雜的"疹尾。
近期了把去年沒寫完的幾篇文章陸續(xù)發(fā)了，還有很早寫的兩篇比較簡單的設(shè)計模式的文章舍悯。都是簡單的記載下了航棱。并且所有的測試代碼都會放到github上面了。

五：浩語

                                           __                                                        
                            __  _  ____ __|  |__ _____    ___
                            \ \/ \/ /  |  \  |  \\__  \  /  _ \   
                             \     /|  |  /   Y  \/ __ \(  <_> )
                              \/\_/ |____/|___|  (____  /\____/ 
                                                    \/     \/          
                                 任何事情都是要靠努力和用心萌衬。