并发编程网 - ifeve.com

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 

try{
SimpleDateFormat sdfDay = new SimpleDateFormat("yyyy-MM-dd");
SimpleDateFormat sdfMins = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
Date now = new Date();
String today = sdfDay.format(now);
String waterStart = today + " 03:00:00";
String waterEnd = today + " 04:00:00";

Date waterStartTime = sdfMins.parse(waterStart);
Date waterEndTime = sdfMins.parse(waterEnd);
}catch (ParseException pe) {
  return XX;
}

优化后3行代码

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

默认值使用Optional

优化前五行

if (null == status) {
   param.put("status", new ArrayList<String>());
  } else {
    param.put("status", status);
  }

优化后一行，使用JDK8的Optional

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

如果是字符串可以用

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 

StringBuffer sblog = new StringBuffer();
sblog.append("waterDriven|sellerId=");
sblog.append(request.getSellerTaobaoId());
sblog.append("|result=");
sblog.append(isSuccess);

 优化后一行 

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 

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

LIST TO MAP

 优化前4行 

Map<String, String> AssetsMetaIdMap = Maps.newHashMap();
        for (AssetsInfoBO assetsInfoBO : request.getAssetsCollectionList()) {
           AssetsMetaIdMap.put(assetsInfoBO.getAssetMetadataId(), assetsInfoBO.getAssetMetadataId());
        }

 优化后1行 

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

 如果key重复会抛出异常

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

减少不需要的判断

 优化前5行 

String requestId = null;
if (null != request.getExtData()) {
    requestId = request.getExtDataValue(REQUEST_ID_KEY);
}
return requestId;

优化后1行

return request.getExtDataValue(REQUEST_ID_KEY);

去掉else

 优化前5行 

if (null != result && StringUtils.isNotBlank(no)) {
     return no;
 } else {
 throw new RuntimeException("XX");
 }

 优化后4行 

if (null != result && StringUtils.isNotBlank(no)) {
     return no;
 } 
 throw new RuntimeException("XX");

不要返回布尔

 优化前5行 

if ("true".equalsIgnoreCase(value.toString())) {
    invoke = true;
 } else {
    invoke = false;
 }

 优化后一行 

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

使用级联

优化前5行 

ParamBO paramBO = new ParamBO();
paramBO.setId(1);
paramBO.setName(”ifeve“);
paramBO.setOld(7);

优化后1行

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