java.lang package are imported by default. Thus you do not need to import java.lang.*; to use them without fully qualifed names.
Consider the System.out.println() method we've been using since the first
day of class.
System is really the java.lang.System class. This class has a public static
field called out which is an instance of the java.io.PrintStream class.
So when you write System.out.println(), you're really calling the println()
method of the out field of the java.lang.System class.