black nightshade - Small fruit

It is actually commonly found in garden, back yard or road side. It is about a two feet height small plantlet. The berry are 4 -5 mm in dia. The fruits are green when not ripe, turns black when it is ripe. It is bitter when green, but sweet like tomato when it is ripe. It is not grown by intention. It just grows on its own. It is called Kaki fruit in kannada language (a south Indian language)