The packages are used for categorization of the same type of classes and interface in a single unit. There is no core or in-built classes that belong to unnamed default package. To use any classes or interface in other class, we need to use it with their fully qualified type name. But some time, we've the need to use all or not all the classes or interface of a package then it's a tedious job to use in such a way discussed. Java supports imports statement to bring entire package, or certain classes into visibility. It provides flexibility to the programmer to save a lot of time just by importing the classes in his/her program, instead of rewriting them.