Simple Packages Demo

Add Directories (Packages)

"packdemo" is our project root directory. Our packages start from this root dir.

The "model" and "test" directory are just simple computer directories.

However, they are also "packages" to Java

\---packdemo classpath dir
	|
	\----model package
	|
	\----test package

Add Java Files In Packages

Add any Java files you want into the two directories.

Here we have one Java file into each package.

\---packdemo classpath dir
	|
	\----model Thing.java
	|
	\----test ThingTest.java

Identifiy Java File With Package Statement

In each Java file we simply add a "package" statement as first statement in file so that identifies the file's owning package.

This file "Thing.java" is in the "model" package.

//Thing.java

package model;

public class Thing {

	public String whoAreYou() {
		return "I am Thing";
	}

}

Identifiy Other Java File With Package Statement

In each Java file we simply add a "package" statement as first statement in file so that identifies the file's owning package.

This file "ThingTest.java" is in the "test" package. Here is the complete source....

ThingTest.java

package test;

public class ThingTest {

Last Step: Import

In each Java file we simply add a "package" statement as first statement in file so that identifies the file's owning package.

This file "ThingTest.java" is in the "test" package.

ThingTest.java

package test;

import model.Thing;

public class ThingTest {

Compiling

This is a basic java compile.

The key is the classpath.

Classpath tells Java where to look for packages (in this example we give it the full path to "packdemo").

echo off
REM compile.bat

REM We can run this script from any dir
REM because classpath will tell Java where to look

set Root=C:\Work\Courses\packdemo

javac -classpath %Root% %Root%\model\Thing.java
javac -classpath %Root% %Root%\test\ThingTest.java

pause

Running

This is a basic java run.

The key again is the classpath.

Classpath tells Java where to look for packages (in this example we give it the full path to "packdemo").

echo off

REM run.bat

REM We can run this script from any dir
REM because classpath will tell Java where to look

set Root=C:\Work\Courses\packdemo

java -classpath %Root% test.ThingTest

pause

Compiling Simplified (Special Case)

If run these commands (or run this script) from the project dir "packdemo" then we can simplify classpath to "." as shown. The dot "." means current directory.

echo off

rem compileFromProjectDir.bat

REM Assuming we are in root dir (where packages live)
REM "." means current dir

javac -classpath "." model\Thing.java
javac -classpath "." test\ThingTest.java

pause

Running Simplified (Special Case)

And running from the project dir (e.g. "packdemo") is similar to the previous compile step.

echo off

REM runFromProjectDir.bat

REM Assuming we are in root dir (where packages live)
REM "." means current dir

java -classpath "." test.ThingTest
pause

Title Here

Wow

Moo

Easy Does It

The kiss steps:

Files are organized into package dirs
Java files are associated with their owning package using a "package" statement line.
We use an "import" statement line to reference classes, etc in other packages.

\---packdemo classpath dir
	|
	\----model Thing.java
	|
	\----test ThingTest.java