Packages

• Packages allow related classed to be grouped together, and help prevent namespace collisions among classes in a large project.
  
• Classes in the package must be public to be useable outside of the package.

• The name of a package (i.e. myPackages.internet.ftp) corresponds to a directory path (myPackages/internet/ftp/) containing a set of classes.
  

Common packages

java.lang   // Used by default
java.net    // Internet reading, transfer, and communication
java.awt    // Abstract windows toolkit, GUIs
java.io     // Streams and files
java.util   // Dates, random numbers, stacks, hash tables

Defining

• Specifies the package that a class is within.
• Define a package at the top of the source file: package PackageName;
• If a package is not defined, the class belong to the package called "Default".
• By default, all classes in an application can access all other classes.

Importing

• Import a single class from a package: import PackageName.ClassName;
• Importing all classes from a package (non-recursively): import PackageName.*;

• If a package is imported, the package name does not have to be used when referring to classes within the package.
• java.lang is imported by default.