A Package:

• Is a named collection of classes and interfaces
• Easily imports related classes into new programs
• Encourages other programmers to reuse software
• Helps avoid naming conflicts or collisions

Give every package a unique name. A class's package name tells the compiler how to locate the class. For example, if a class instantiates a Scanner object, the Java compiler must be directed to the package that contains the Scanner class, that is, to java.util.

When creating classes for others to use:

• Protect your work
  • Do not provide users with source code in files with .java extensions
  • Provide users with compiled files with .class extensions
• Include package statement at beginning of class file
  • Place compiled code into indicated folder

A class that will be placed in a package for others to use must be public. If a class is not public, it can be used only by other classes within the same package.

If you do not specify a package for a class, it is placed in an unnamed default package.

You cannot import more than one package in one statement; for example, if multiple packages are stored in a folder named com, you cannot import them with the statement import com.*. The import statement only imports files from one folder at a time.

The package statement, import statements, and comments are the only statements that appear outside class definitions in Java program files.