Java

Package creates a namespace, different packages can have classes with same package
Allow types within the package to have unrestricted access to one another yet still restrict access for types outside the package

//Car.java
package edu.ecsu.cs;

public class Car
{
	private String maker;

	public Car(String m)
	{
		maker = m;
	}

	public String toString()
	{
		return maker;
	}

	public static void main(String args[])
	{
		Car c = new Car("Buick");

		System.out.println(c);

		Bike b = new Bike("Phenix");

		System.out.println(b);
	}
}

//Bike.java
package edu.ecsu.cs;

class Bike
{
	private String maker;

	public Bike(String m)
	{
		maker = m;
	}

	public String toString()
	{
		return maker;
	}

	public static void main(String args[])
	{
		Car c = new Car("Buick");

		System.out.println(c);
	}
}

javac -d [outputPat] [*.java]
javac -d . Car.java

Refer to the member by its fully qualified name
Import the package member
Import the member's entire package

//CarUse.java
import edu.ecsu.cs.*;

public class CarUse
{
	public static void main(String args[])
	{
		Car c = new Car("Honda");

		System.out.println(c);
		
		//not able to use Bike since it is not a public class
		//Bike b = new Bike("Phenix");

		//System.out.println(b);
	}
}

Order of searching classes
- Runtime classes (basically, rt.jar in $JRE_HOME/lib`)
- Extension classes (some JARs in $JRE_HOME/lib/ext`)
- Classpath, in order. There are four possibilities for specifying classpath:
  - If -jar was specified, then that JAR is in the classpath. Whatever classpath is declared as classpath in META-INF/MANIFEST.MF is also considered
  - Else, if -cp was specified, that is the classpath
  - Else, if $CLASSPATH is set, that is the classpath
  - Else, the current directory from which java has been launched is the classpath
% CLASSPATH=/home/george/java/classes; export CLASSPATH
javac *.java -classpath path_1:path_2, figure out class path, containing a list of directories or archive files, separated by :
- javac -cp "../P.jar:./" CarUse
java -classpath path_1:path_2 CarUse, add pathes containing all classes needed
- java -cp "../P.jar:./" CarUse