making a java package in the command line

There are three parts to it: (1) create directory structure; (2) indicate package in java file; (3) compile it.

For example, if you want to create package com.mycompany.myproject, then you need to start in the base directory for your project and then:

(1) create directory com/mycompany/myproject

(2) create java files in that directory, stating package com.mycompany.myproject in them;

(3) compile the files, for example, with javac -cp . com/mycompany/myproject/*.java

You may want to specify a different output directory so as to not mix sources and compiled classes.

If you need to use external libraries (.jar files) to compile, then you need to use -cp or -classpath command-line parameter to javac tool to specify them, e.g.

javac -cp .:some_library.jar:lib/another_library.java com/mycompany/myproject/*.java

It may be a good idea to put all external libraries in one place, e.g. lib subdirectory of your main project directory. And, by the way, the above javac command assumes unix-like environment. If you're on Windows, then you'll need to use ; for path separation.

packages are just directories on the filesystem. so your package: com.mycompany.util corresponds to a directory com/mycompany/util.

When running and compiling etc your current workding directory should be where that top directory is located.

To include libraries, include them in your classpath when compiling and running. For example make a Project directory myproject and under that have your java-files and packages under myproject/src/ and libraries that you use under myproject/libs/ Then when your current workding directory is myproject execute java -cp .:libs/*.jar or the same with javac.

But I suggest you look into using ant or maven.

You can get along just fine on the command line by using a packaging tool such as Ant or Maven. Maven is especially handy because it is a higher level tool that already knows how to build various project types: command-line apps, webapps, libraries, etc. It also handles library dependencies by downloading them from repositories.