Can I fly to US on H1B visa 2 weeks before joining employer?

Hello, I have H1B stamped through a US company and is valid from May 21 2018. I am currently in India. The joining date is 16th July (H1B start date is May 21). Can I enter US on July 1st & then join the employer on the given date of 16th July? Can I remain without employment for those 15 days?

If not, then in how many days I need to join them? Thanks Niket