史蒂夫.喬布斯說，”復雜的終極境界是簡單“，同樣的優雅的代碼一定是精簡明了，可讀性好。

使用LocalDate和LocalDateTime

LocalDate精確到日期，LocalDateTime精確到時分秒。優化前14行代碼

1. try {

2. SimpleDateFormat sdfDay = new SimpleDateFormat("yyyy-MM-dd");

3. SimpleDateFormat sdfMins = new SimpleDateFormat("yyyy-MM-dd HHss");

4. Date now = new Date();

5. String today = sdfDay.format(now);

6. String waterStart = today + " 0300";

7. String waterEnd = today + " 0400";

8. Date waterStartTime = sdfMins.parse(waterStart);

9. Date waterEndTime = sdfMins.parse(waterEnd);

10. } catch (ParseException pe) {

11. return XX;

12. }

優化后3行代碼

1. LocalDateTime now = LocalDateTime.now();

2. LocalDateTime waterStart = LocalDateTime.of(now.getYear(), now.getMonth(),now.getDayOfMonth(),3,0);

3. LocalDateTime waterEndTime =LocalDateTime.of(now.getYear(), now.getMonth(),now.getDayOfMonth(),4,0);

默認值使用Optional

優化前五行

1. if (null == status) {

2. param.put("status", new ArrayList<String>());

3. } else {

4. param.put("status", status);

5. }

優化后一行，使用JDK8的Optional

1. Optional.ofNullable(status).orElse(new ArrayList<String>());

如果是字符串可以用

1. StringUtils.defaultIfEmpty(status,"")

字符串累加

字符串只要不在for循環里累加，可以直接用+號，因為編譯成字節碼后會變成StringBuilder，如果在for循環里面用+號會生成多個StringBuilder，所以在for循環里累加最好在循環外創建StringBuilder。優化前五行

1. StringBuffer sblog = new StringBuffer();

2. sblog.append("waterDriven|sellerId=");

3. sblog.append(request.getSellerTaobaoId());

4. sblog.append("|result=");

5. sblog.append(isSuccess);

優化后一行

1. String sblog="waterDriven|sellerId="+request.getSellerTaobaoId()+"|result="+isSuccess;

以上場景用逗號和等號連接數據，使用GUAVA的Joiner更精簡，可讀性更好

1. String sblog=Joiner.on("|").withKeyValueSeparator("=").join(ImmutableMap.of("sellerId", request.getSellerTaobaoId(), "result", isSuccess))

LIST TO MAP

優化前4行

1. Map<String, String> AssetsMetaIdMap = Maps.newHashMap();

2. for (AssetsInfoBO assetsInfoBO : request.getAssetsCollectionList()) {

3. AssetsMetaIdMap.put(assetsInfoBO.getAssetMetadataId(), assetsInfoBO.getAssetMetadataId());

4. }

優化后1行

1. Map<String, String> AssetsMetaIdMap = request.getAssetsCollectionList().stream().collect(Collectors.toMap(Hosting::getAssetMetadataId, Hosting::getAssetMetadataId));

如果key重復會拋出異常

1. Exception in thread "main" java.lang.IllegalStateException: Duplicate key 80000

減少不需要的判斷

優化前5行

1. String requestId = null;

2. if (null != request.getExtData()) {

3. requestId = request.getExtDataValue(REQUEST_ID_KEY);

4. }

5. return requestId;

優化后1行

1. return request.getExtDataValue(REQUEST_ID_KEY);

去掉else

優化前5行

1. if (null != result && StringUtils.isNotBlank(no)) {

2. return no;

3. } else {

4. throw new RuntimeException("XX");

5. }

優化后4行

1. if (null != result && StringUtils.isNotBlank(no)) {

2. return no;

3. }

4. throw new RuntimeException("XX");

不要返回布爾

優化前5行

1. if ("true".equalsIgnoreCase(value.toString())) {

2. invoke = true;

3. } else {

4. invoke = false;

5. }

優化后一行

1. invoke = "true".equalsIgnoreCase(value.toString());

使用級聯

優化前5行

1. ParamBO paramBO = new ParamBO();

2. paramBO.setId(1);

3. paramBO.setName(”ifeve“);

4. paramBO.setOld(7);

優化后1行

1. new ParamBO().withId(1).withName("ifeve").withOld(7);

-End-

審核編輯 ：李倩