There is one exception to the import rule. All classes in the
java.lang
package are imported by default. Thus you do
not need to import java.lang.*;
to use them without
fully qualified 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.