Java基础知识汇总

如何计算rt
(1)Stopwatch stopwatch = Stopwatch.createStarted();
(2)stopwatch.stop();
(3)rt就等于 stopwatch.elapsed(TimeUnit.MILLISECONDS)


如何判断一个object非空
if(Objects.nonNull(systemInfo)){
    utdid = systemInfo.getUtdid();
}


如何判断一个集合非空
if (CollectionUtils.isNotEmpty(query.getModuleIds())){
     moduleIds = Joiner.on(",").join(query.getModuleIds());
}