《java開(kāi)發(fā)手冊(cè)》中:

況且日常開(kāi)發(fā)時(shí)遇到一推的if-else著實(shí)讓人頭疼!

so，現(xiàn)在開(kāi)始改造

一、衛(wèi)語(yǔ)句

衛(wèi)語(yǔ)句就是把復(fù)雜的條件表達(dá)式拆分成多個(gè)條件表達(dá)式，即代碼邏輯先考慮失敗、異常、中斷、退出等直接返回的情況，以方法多個(gè)出口的方式，解決代碼中判斷分支嵌套的問(wèn)題，這是逆向思維的體現(xiàn)

比如:

if (type == 0) {

code...

}else if (type == 1) {

code...

} else if (type == 2) {

code...

} else {

otherCode...

}

可以改造為:

if (type == 0) {

code...

return;

}

if (type == 1) {

code...

return;

}

if (type == 2) {

code...

return;

}

otherCode....

二、策略模式

現(xiàn)在有個(gè)需求，根據(jù)用戶的類型來(lái)展示不同的內(nèi)容，我們將其具體化為一段代碼:

if ("新客戶".equals(userType)) {

showNewContent...;

}else if("VIP客戶".equals(userType)){

showVIPContent...;

}else if ("白金客戶".equals(userType)) {

showPlatinaContent...;

}else if ("黑卡用戶".equals(userType)){

showBlackCardContent...;

}else if ("回歸用戶".equals(userType)){

showComeBackContent...;

}else {

showOtherContent...;

}

這樣看是看不出來(lái)有何不妥的，但是想想，要推薦的內(nèi)容何止這么點(diǎn)代碼，如果不管不顧，就這么寫(xiě)，到時(shí)候?qū)懲甏a回過(guò)頭來(lái)，自己都得看老半天才能看懂，何論后期維護(hù)的人呢，而且要是后期又添加了一種新的用戶類型，那是不是又要寫(xiě)一個(gè)else-if插在中間，然后又增量添加一推代碼，這樣豈不是太麻煩了?，反正強(qiáng)迫癥肯定是受不了的

策略模式改造:

1.定義一個(gè)策略接口

public interface ShowStrategy{

void showContentByUserType();

}

2.定義多個(gè)具體的策略實(shí)現(xiàn)

public class ShowNewContentStrategy implements ShowStrategy {

@Override

public void showContentByUserType() {

System.out.println("展示新用戶內(nèi)容");

}

}

public class ShowVIPContentStrategy implements ShowStrategy {

@Override

public void showContentByUserType() {

System.out.println("展示VIP用戶內(nèi)容");

}

}

public class ShowPlatinaContentStrategy implements ShowStrategy {

@Override

public void showContentByUserType() {

System.out.println("展示白金用戶內(nèi)容");

}

}

public class ShowBlackCardContentStrategy implements ShowStrategy {

@Override

public void showContentByUserType() {

System.out.println("展示黑卡用戶內(nèi)容");

}

}

public class ShowComeBackContentStrategy implements ShowStrategy {

@Override

public void showContentByUserType() {

System.out.println("展示回歸用戶內(nèi)容");

}

}

3.定義一個(gè)策略使用的client

public class ShowStrategyClient {

//持有一個(gè)策略接口引用

private ShowStrategy showStrategy;

//注入

public ShowStrategyClient(ShowStrategy showStrategy) {

this.showStrategy = showStrategy;

}

//策略client的方法

public void clientMethod(){

showStrategy.showContentByUserType();

}

}

4.外部使用

回到我們的需求，用寫(xiě)好的策略模式重構(gòu)

public void test() {

//1.創(chuàng)建新用戶的內(nèi)容展示策略

ShowStrategy newContentStrategy = new ShowNewContentStrategy();

//2.創(chuàng)建策略客戶端,注入新用戶策略實(shí)現(xiàn)

ShowStrategyClient showStrategyClient = new ShowStrategyClient(newContentStrategy);

showStrategyClient.clientMethod();

}

三、狀態(tài)模式

繼續(xù)引用我們?cè)凇岸?、策略模式”中的例?/p>

狀態(tài)模式改造:

1.定義一個(gè)狀態(tài)行為接口

interface UserState {

void showNewContent(ShowStateClient client);

void showVIPContent(ShowStateClient client);

void showPlatinaContent(ShowStateClient client);

void showBlackCardContent(ShowStateClient client);

void showComeBackContent(ShowStateClient client);

}

2.定義多個(gè)具體的狀態(tài)實(shí)現(xiàn)

public class ShowNewContentState implements UserState {

@Override

public void showNewContent(ShowStateClient client) {

System.out.println("展示新用戶內(nèi)容");

}

@Override

public void showVIPContent(ShowStateClient client) {

System.out.println("用戶狀態(tài)錯(cuò)誤");

}

@Override

public void showPlatinaContent(ShowStateClient client) {

System.out.println("用戶狀態(tài)錯(cuò)誤");

}

@Override

public void showBlackCardContent(ShowStateClient client) {

System.out.println("用戶狀態(tài)錯(cuò)誤");

}

@Override

public void showComeBackContent(ShowStateClient client) {

System.out.println("用戶狀態(tài)錯(cuò)誤");

}

}

public class ShowVIPContentState implements UserState {

@Override

public void showNewContent(ShowStateClient client) {

System.out.println("用戶狀態(tài)錯(cuò)誤");

}

@Override

public void showVIPContent(ShowStateClient client) {

System.out.println("展示VIP用戶內(nèi)容");

}

@Override

public void showPlatinaContent(ShowStateClient client) {

System.out.println("用戶狀態(tài)錯(cuò)誤");

}

@Override

public void showBlackCardContent(ShowStateClient client) {

System.out.println("用戶狀態(tài)錯(cuò)誤");

}

@Override

public void showComeBackContent(ShowStateClient client) {

System.out.println("用戶狀態(tài)錯(cuò)誤");

}

}

public class ShowPlatinaContentState implements UserState {

@Override

public void showNewContent(ShowStateClient client) {

System.out.println("用戶狀態(tài)錯(cuò)誤");

}

@Override

public void showVIPContent(ShowStateClient client) {

System.out.println("用戶狀態(tài)錯(cuò)誤");

}

@Override

public void showPlatinaContent(ShowStateClient client) {

System.out.println("展示白金用戶內(nèi)容");

}

@Override

public void showBlackCardContent(ShowStateClient client) {

System.out.println("用戶狀態(tài)錯(cuò)誤");

}

@Override

public void showComeBackContent(ShowStateClient client) {

System.out.println("用戶狀態(tài)錯(cuò)誤");

}

}

public class ShowBlackCardContentState implements UserState {

@Override

public void showNewContent(ShowStateClient client) {

System.out.println("用戶狀態(tài)錯(cuò)誤");

}

@Override

public void showVIPContent(ShowStateClient client) {

System.out.println("用戶狀態(tài)錯(cuò)誤");

}

@Override

public void showPlatinaContent(ShowStateClient client) {

System.out.println("用戶狀態(tài)錯(cuò)誤");

}

@Override

public void showBlackCardContent(ShowStateClient client) {

System.out.println("展示黑卡用戶內(nèi)容");

}

@Override

public void showComeBackContent(ShowStateClient client) {

System.out.println("用戶狀態(tài)錯(cuò)誤");

}

}

public class ShowComeBackContentState implements UserState {

@Override

public void showNewContent(ShowStateClient client) {

System.out.println("用戶狀態(tài)錯(cuò)誤");

}

@Override

public void showVIPContent(ShowStateClient client) {

System.out.println("用戶狀態(tài)錯(cuò)誤");

}

@Override

public void showPlatinaContent(ShowStateClient client) {

System.out.println("用戶狀態(tài)錯(cuò)誤");

}

@Override

public void showBlackCardContent(ShowStateClient client) {

System.out.println("用戶狀態(tài)錯(cuò)誤");

}

@Override

public void showComeBackContent(ShowStateClient client) {

System.out.println("展示回歸用戶內(nèi)容");

}

}

3.定義一個(gè)狀態(tài)使用的client

public class ShowStateClient {

private UserState userState;

public void setUserState(UserState userState){

this.userState = userState;

}

public UserState getUserState(){

return userState;

}

public void showNewContent() {

userState.showNewContent(this);

}

public void showVIPContent() {

userState.showVIPContent(this);

}

public void showPlatinaContent() {

userState.showPlatinaContent(this);

}

public void showBlackCardContent() {

userState.showBlackCardContent(this);

}

public void showComeBackContent() {

userState.showComeBackContent(this);

}

}

4.外部使用

public static void main(String[] args) {

ShowStateClient client = new ShowStateClient();

client.setUserState(new ShowNewContentState());

client.showNewContent();

client.showVIPContent();

client.showPlatinaContent();

client.showBlackCardContent();

client.showComeBackContent();

}

個(gè)人覺(jué)得狀態(tài)模式過(guò)于臃腫，用處反而沒(méi)有特別突出，不過(guò)也許是我沒(méi)有遇到合適的場(chǎng)景或者理解有誤吧!

標(biāo)簽：語(yǔ)句,void,System,模式,用衛(wèi),client,println,ShowStateClient,public

來(lái)源： https://www.cnblogs.com/yibeijingdoujiang/p/11393380.html

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