Classes in the same package are implicitly imported into source-code files of other classes in the same package.

Classes System and String are in the package java.lang

An import declaration is not required if you always refer to a class via its fully qualified class name.

We have to use the Java.lang classes by explicitly importing them.

Import declarations involve a package name followed by a dot and the class name.

When classes that are compiled in the same directory on disk are in the same package, this is known as the default package.