Additional Java Syntax - Building Java Programs: A Back to Basics Approach - page 1132

statement at the top of the file, even before any import statements or the class's
header. A package declaration has the following syntax:
package <name> ;
For example, to specify that the class CardGame belongs to the homework4 pack-
age, you would write the following statement at the top of the CardGame.java file:
package homework4;
import java.io.*;
import java.util.*;
// This class represents the main card game logic.
public class CardGame {
...
}
Packages may be nested, indicated by dots. The packages in the Java class
libraries are nested at least two levels deep, such as java.util or java.awt.event .
For example, to specify that a graphical user interface file for Homework 4 belongs
to the gui subpackage within the homework4 package, you would write the following
statement:
package homework4.gui;
...
Packages are reflected by the directory structure of the files in your Java project.
For example, if a file claims to belong to the homework4 package, it must be placed
in the homework4/ directory relative to the root directory of your project. A file in
the homework.gui package must be in the homework4/gui directory relative to the
project's root.
If you write classes that are part of different packages and a class from one pack-
age wants to use a class from another, you must use an import statement for the com-
piler to find the classes. Remember that packages are not nested, so importing the
homework4 package does not automatically import homework4.gui and vice versa.
package general;
import homework.*;
import homework.gui.*;
...
Packages are generally not necessary for small projects, though some editors add
them to the top of all files automatically. Users of basic Java IDEs or text editors