几个不错的代码瘦身优化案例

史蒂夫.乔布斯说，”复杂的终极境界是简单“，同样的优雅的代码一定是精简明了，可读性好。

使用LocalDate和LocalDateTime

LocalDate精确到日期，LocalDateTime精确到时分秒。优化前14行代码

1. try {

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

3.    SimpleDateFormat sdfMins = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");

4.    Date now = new Date();

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

6.    String waterStart = today + " 03:00:00";

7.    String waterEnd = today + " 04:00:00";

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

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

10. } catch (ParseException pe) {

11.    return XX;

12. }

优化后3行代码

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);

默认值使用Optional

优化前五行

1. if (null == status) {

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

3. } else {

4.    param.put("status", status);

5. }

优化后一行，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循环里累加，可以直接用+号，因为编译成字节码后会变成StringBuilder，如果在for循环里面用+号会生成多个StringBuilder，所以在for循环里累加最好在循环外创建StringBuilder。优化前五行

1. StringBuffer sblog = new StringBuffer();

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

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

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

5. sblog.append(isSuccess);

优化后一行

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

以上场景用逗号和等号连接数据，使用GUAVA的Joiner更精简，可读性更好

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

LIST TO MAP

优化前4行

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

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

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

4. }

优化后1行

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

如果key重复会抛出异常

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

减少不需要的判断

优化前5行

1. String requestId = null;

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

3.    requestId = request.getExtDataValue(REQUEST_ID_KEY);

4. }

5. return requestId;

优化后1行

1. return request.getExtDataValue(REQUEST_ID_KEY);

去掉else

优化前5行

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

2.     return no;

3. } else {

4.     throw new RuntimeException("XX");

5. }

优化后4行

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

2.     return no;

3. }

4. throw new RuntimeException("XX");

不要返回布尔

优化前5行

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

2.    invoke = true;

3. } else {

4.    invoke = false;

5. }

优化后一行

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

使用级联

优化前5行

1. ParamBO paramBO = new ParamBO();

2. paramBO.setId(1);

3. paramBO.setName(”ifeve“);

4. paramBO.setOld(7);

优化后1行

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

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