Groupon is the daily deal websites that serves many major international markets, offering one coupon per day in each these markets. You can’t go anywhere online these days without spotting a Groupon ad. It's theory as we all know - the social features of its deep-discount offers for local merchants — a certain size group had to sign up in order for the deal to be “on” has been the reason for the huge success.
Java is a general-purpose, concurrent, class-based, object-oriented computer programming language that is specifically designed to have as few implementation dependencies as possible. It is intended to let application developers "write once, run anywhere" (WORA), meaning that code that runs on one platform does not need to be recompiled to run on another.
An open source license is a copyright license for computer software that allows the source code to be freely, that is by anyone for any purpose, used, modified and shared. This allows end users to review and modify the source code for their own customization, curiosity or troubleshooting needs.