Java Outside In - Development Environments

In Chapter 1 of the text we discussed the life cycle of a computer program:

Imagine what the program will do
Design it
Write the program in some language (Java, of course)
Compile
Run and test
Imagine improvements

Steps 1, 2 and 6 you can do in your head, but steps 3, 4 and 5 need to be done on a computer. For step 3 you need a word processor (text editor) of some kind. For step 4 you need the Java compiler. For step 5 you need the Java Virtual Machine. To work on the examples in Java Outside In you will need access to the Java code discussed in the text.

There are three ways you might arrange to have all these software tools available on your computer. Some combination will work for you.

If you are using Java Outside In as the text for a course, your instructor will explain how you are to edit, compile and test your programs in the environment he or she has set up for the course.
You can install Java on your computer and then use any text editor you wish.
You can install an integrated development environment - a single software application that supports the edit/compile/run sequence in the software development cycle.

Just get Java ...

The Java compiler and the Java Virtual Machine are available free for Windows, Solaris or Linux at http://java.sun.com/. You should download the latest production version of the Java^TM2 Platform, Standard Edition (J2SE^TM) from http://java.sun.com/j2se/downloads.html.

If you are using a Macintosh computer you will find these tools already installed as part of Mac OS X. For earlier versions of the Macintosh operating system, search the web for information.

Once you have installed Java you may write your programs using any word processor you like. On a Windows PC Microsoft Word, or just plain Notepad will do. On Unix or Linux you will use either vi or emacs as an editor. Compile and run your program from any command prompt.

You can get a free emacs editor for Windows, Unix/Linux or Mac OS X at http://www.xemacs.org/Download/. Warning: emacs is a powerful programming editor but not easy for beginners.

Integrated environments

In the real software world editors and compilers are usually combined in an IDE - an integrated development environment. The editor will display language keywords and comments in different colors. It may prettyprint for you. You can compile and run programs without leaving the environment, which will help you locate errors in your code. Here are several you might want to consider:

Sun's Java IDE (it used to be called Forte). You can find it at http://wwws.sun.com/software/sundev/jde/. The Community Edition (more than adequate for this text!) is free.
JBuilder, from Borland (http://www.borland.com/) is a popular Java IDE. The personal edition is free.
Bluej, at http://www.bluej.org/, a Java IDE written specifically for students. It's free too.
Editplus, at http://www.editplus.com/. This is shareware (that is, use it free for a while and then pay a small fee if you are a moral person).

A Google search for "Free Java IDE" will turn up more candidates. Some of these environments may come with Java installed, in which case you won't need to get a copy separately.

Using classes from the library

The Java compiler and the Java Virtual Machine know how to find all the classes (like String) that come with the Java library. But there are times when your program needs access to other classes that you have not written. In particular, many of the programs in Java Outside In use the Terminal class. You can make such classes available to your program in several ways.

If Java Outside In is the text for your programming course, your instructor will give you appropriate instructions, or will have made the classes available to you without telling you how she did it.
You can copy the source code for the classes you need to the directory or folder in which you are working and compile it right there. The advantage of this strategy is that it's easy and easy to understand. The disadvantage is that it might tempt you to try to make your program work by modifying that source code in those classes meant only to be used, not modified.
A slightly better strategy is just to copy the .class files for the classes you need to the directory in which you are working. The disadvantage of this strategy is that it clutters your working directory, and the file system, with copies of the class files.
Both the previous strategies suffer from another serious problem. If for some reason the class you need access to must be changed - perhaps to fix a bug - when that change is made to the original your copies become out of date. You can avoid this problem if your computer allows you to create shortcuts or aliases or links to files. Then the directory in which you are working has just a reference to the original, not a copy. If the original is changed your reference is up to date.
A better solution is to tell Java where to look for class files. If you do nothing special, Java looks first in the directory or folder in which you are working, then in the Java library. But you can tell it to look elsewhere too. For example, suppose your code in file Whatever.java creates a Terminal object. In a Windows system you might put Terminal.class in folder C:\joi\classes. Then you could invoke Java this way
```
	> javac -classpath .;C:\joi\classes Whatever.java

	> java -classpath .;C:\joi\classes Whatever
```
to compile and run Whatever.java.
The best solution is probably to tell Java just once where to look. You do that by setting the environment variable CLASSPATH .
On Windows you might
- Create a folder for class files for those classes you will want to use - perhaps C:\joi\classes .
- Copy the Terminal.class file from terminal\Terminal.class on this CD to that folder.
- Find the screen for setting Environment Variables on the Advanced pane of your System window and set the CLASSPATH environment variable on your computer to .;C:\joi\classes . This tells Java to look for classes (such as Terminal) both in the current working folder ( . ) and in C:\joi\classes . (You may make the list of folders in the classpath as long as you like.)
- Compile and run with the java and javac commands, which will find the classes in the CLASSPATH automatically.
In a Unix (or Linux) system, replace the file separator \ by / and the path separator ; by . and set the CLASSPATH environment variable in your login script.
If you are using an IDE, you may be able to set the class path in the IDE itself
The most important class you will need is the Terminal
Almost all of the programs in Java Outside In use a special program (a class actually) called Terminal to manage output to the screen and input from the keyboard. You must have the Terminal in your environment in order to run those programs.
The source code is on this CD in file \terminal\Terminal.java. The class file is in file \terminal\Terminal.class for you to copy.
There are two ways you arrange to use a Terminal.
1. One way is to copy the source file for the Terminal and for any other classes you need to the directory or folder in which you are working. For example, to play with the banking example from Chapter 1 you would copy both \terminal\Terminal.java and Bank.java and BankAccount.java from \joi\1\bank.
  But this can become cumbersome after a while.
2. A better way to use Terminal is to put Terminal.class in your classpath, as discussed above. Then it is always available to you.

Off you go. Have fun!