場(chǎng)景：當(dāng)我們接收到一些數(shù)據(jù)需要對(duì)其進(jìn)行處理時(shí)，由于它們來(lái)自于不同的渠道（如：騰訊，頭條），不同渠道所需的處理方式不同，下面我們寫(xiě)一個(gè)簡(jiǎn)單Demo來(lái)實(shí)現(xiàn)該的場(chǎng)景。

解決思路

public?abstract?class?GeneralChannelRule?{
?public?abstract?void?process();
}

2、編寫(xiě)一個(gè)騰訊的規(guī)則類，定義具體對(duì)于騰訊渠道數(shù)據(jù)的處理邏輯

public?class?TencentChannelRule?extends?GeneralChannelRule
???@Override
????public?void?process()?{
????????//?Tencent處理邏輯
????}
}

3、編寫(xiě)一個(gè)頭條的規(guī)則類，定義具體對(duì)于頭條數(shù)據(jù)的處理邏輯

public?class?TouTiaoChannelRule?extends?GeneralChannelRule
???@Override
????public?void?process()?{
????????//?TouTiao處理邏輯
????}
}

4、建立一個(gè)簡(jiǎn)單的枚舉類

public?enum?ChannelRuleEnum?{
????/**
?????*?頭條
?????*/
????TOUTIAO("TOUTIAO"),
????/**
?????*?騰訊
?????*/
????TENCENT("TENCENT"),
????;
??....
}

5、使用規(guī)則對(duì)數(shù)據(jù)進(jìn)行處理。

public?static?void?main(String[] args) {
????????//這里我們模擬接收到的數(shù)據(jù)，其渠道為為TOUTIAO，來(lái)自頭條的數(shù)據(jù)
????????String sign = "TOUTIAO";
????????GeneralChannelRule rule;
????????//根據(jù)對(duì)應(yīng)渠道獲取對(duì)應(yīng)的具體規(guī)則實(shí)現(xiàn)類
????????if?(ChannelRuleEnum.TENCENT.code.equals(sign)) {
????????????rule = new?TencentChannelRule();
????????} else?if?(ChannelRuleEnum.TOUTIAO.code.equals(sign)) {
????????????rule = new?TouTiaoChannelRule();
????????} else?{
????????????//匹配不到
????????}
????????//執(zhí)行
????????rule.process();
????}

新的思路

public?enum?ChannelRuleEnum?{

????/**
?????*?頭條
?????*/
????TOUTIAO("TOUTIAO",new?TouTiaoChannelRule()),
????/**
?????*?騰訊
?????*/
????TENCENT("TENCENT",new?TencentChannelRule()),
????;

????public?String?name;

????public?GeneralChannelRule?channel;

????ChannelRuleEnum(String?name,?GeneralChannelRule?channel)?{
????????this.name?=?name;
????????this.channel?=?channel;
????}

??//匹配
????public?static?ChannelRuleEnum?match(String?name){
????????ChannelRuleEnum[]?values?=?ChannelRuleEnum.values();
????????for?(ChannelRuleEnum?value?:?values)?{
????????????if(value.name.equals(name)){
????????????????return?value;
????????????}
????????}
????????return?null;
????}
????public?String?getName()?{
????????return?name;
????}

????public?GeneralChannelRule?getChannel()?{
????????return?channel;
????}
}

2、改寫(xiě)程序

public?static?void?main(String[]?args)?{
????????String?sign?=?"TOUTIAO";
????????ChannelRuleEnum?channelRule?=?ChannelRuleEnum.match(sign);
????????GeneralChannelRule?rule?=?channelRule.channel;
????????rule.process(sign);
????}

解析：通過(guò)使用枚舉類，在枚舉中將 key 與 規(guī)則具體實(shí)現(xiàn)進(jìn)行綁定。通過(guò)改變：

可以減少if -else使得代碼更加優(yōu)雅 如果需要新增渠道，我們只需要在編寫(xiě)具體規(guī)則實(shí)現(xiàn)類并繼承GeneralChannelRule抽象類，并在枚舉類中新增的枚舉，而不需要改動(dòng)到原先的任何代碼。這符合了開(kāi)發(fā)封閉原則。

最后

以上是通過(guò)枚舉來(lái)巧妙干掉if-else的方案，對(duì)于減少 if-else 還有很多有趣的解決方案（如：狀態(tài)設(shè)計(jì)模式等），感興趣的朋友去查閱相關(guān)的資料。