Question

Why do we use reverse domain name like com.something. or org.something. structure for java packages?
I understand this brings in some sort of uniqueness, but why do we need this uniqueness?

Answer 1

Globally unique package names avoid naming collisions between libraries from different sources. Rather than creating a new central database of global names, the domain name registry is used. From the JLS:

The suggested convention for
generating unique package names is
merely a way to piggyback a package
naming convention on top of an
existing, widely known unique name
registry instead of having to create a
separate registry for package names.