Using the JDK 

This Web page will help you explore the "mechanics" of Java programming. You'll learn how to: 
  • Download and install the JDK from Sun
  • How to set up your Java programming environment
  • How to compile, edit, and run your programs
The examples here all asume you are running Windows95/98, NT, ME, or W2K. The process for downloading and installing the IBM version of the JDK is almost identical. 
 
For Macintosh Users
If you are programming on a Mac, you'll need to download both the Macintosh Runtime for Java [MRJ 2.1.2] as well as the MRJ SDK. Once you've installed them, just follow the directions. [One hint that may help you: the Mac tools--javac, etc.--are supposed to be all drag'n'drop; rather than typing in commands like javac, you simply edit your source code and then drop it on the javac icon. In fact, I've had some difficulty getting this to work. Instead, I've found that I need to create a folder and put both my source code and a copy of the javac compiler into the folder.]

I'm always on the lookout for instructions and screenshots if you work in the Mac environment.

Download and Install the JDK 

There are several versions of the Sun JDK. These are numbered in major and minor versions. The major versions are: 
  • Java 1.0: This is the original version of Java and is widely supported in all Web browsers that run Java. Java 1.0 had about 2,000 different methods in about 200 different classes.

    •  
  • Java 1.1: The first major revision of Java. The major change was a different "event model". [Simply a different way of handling interaction with the user]. Java 1.1 is supported on IE4 and above as well as Navigator 4.06 and above for Unix and Windows. Java 1.1 is not supported on Navigator for the Mac; there you must use IE. Java 1.1 has a little more than 5,000 different methods in about 500 classes.

    •  
  • Java 1.3 [Also called the Java 2 Platform]. This is the latest release of Java, and it doesn't run on any browsers [not even Sun's all-Java browser, Hot Java]. Instead, Sun provides the "Java Plugin" if you want to run Java applets. Java 2 contains about 20,000 methods in about 1,500 classes.
To complete this class, you must use, at least, Java 1.1. You can download Java 2 if you like, but we will not be making use of the new Java 2 features. [You can write Java 1.0 and 1.1 code using both Java 1.1 and Java 1.2 JDKs] 

There are also minor versions of Java 1.1. These versions are numbered with a third digit like this:1.1.2, 1.1.3,...1.1.8. Your textbook has version 1.1.2 on CD-ROM. This is revision 2 of JDK 1.1. You can use that to complete all of the exercises in the book, but I'd suggest you download the latest version of the Java 1.1 JDK, which is 1.1.8. The minor version updates of the Java 1.1 are bug fixes; they don't add any new features. 

Step 1: Locate the JDK 

For Windows and Solaris, you can download the JDK directly from Sun Microsystems for free. The link for the Windows version of the JDK 1.1.8 is at: 
http://www.javasoft.com/products/jdk/1.1/download-jdk-windows.html
You can download the Java 2 Platform, Standard Edition Software Development Kit (J2SESDK) link for free as well. That link, for the Windows version of SDK 1.3, is: 
http://www.javasoft.com/j2se/1.3/download-windows.html
If you're undecided about which one to download, the size might make a difference. JDK 1.8 is about 9MB, while the Java 2 download is around 30MB. 

Step 2: Select Your Download 

Once you've arrived at the Sun site, scroll on down the page until you locate the download area. For JDK 1.1, it will look like this: 
Download the Sun JDK 1.1.8
If you are using a slow or otherwise unreliable connection, you may want to download the JDK as small pieces, each of which will fit on a 1.44 floppy disk. Make sure you carefully follow the instructions for reassembling them if you do so. 

If you elect to download the Java 2 SDK, you will have to scroll past a whole bunch of advertisements for various IDEs [Integrated Development Environments] before you get to the actual SDK download area at the bottom of the page. The Java 2 SDK download area looks like this: 

Download area for Java 2 SDK
When you click on the Continue button, you'll be asked to agree to the usual inscrutable Web licensing agreement. [You'll also be asked to agree once again before you install the JDK]. Since you can't download or install without agreeing, you may as well go ahead. 
License agreement to download the Sun JDK

Step 3: Download and Save 

Once you agree, you'll be shown to a screen where you can begin the final download, shown below. 

Note the name and size of the download file. Write down this information so you can compare it to what actually is downloaded to your machine. If the size of the downloaded file is different that what is shown, then a problem occured during download and you'll have to try again. If the name is different [some browsers will rename downloaded files] you'll simply have to rename the file after it's downloaded. 

FTP/HTTP download button when downloading the Sun JDK
Once you've finished, then click on either the FTP or HTTP download buttons. [FTP is faster, but the Sun FTP servers seem to be a little busier. If your browser can't seem to connect to the FTP server, then try the HTTP]. 

Select a location for the downloaded file somewhere on your local hard disk, and sit back and enjoy a cup of coffee while it downloads. Make sure you remember where you downloaded the file, however. 

Save Downloaded File dialog with JDK 1.1 file being downloaded for Windows
Afte the file is downloaded, you're ready to begin the install. 

Step 4: Install the JDK 

After what you've gone through up to this point, installation itself is rather anticlimatic. Make sure you have enough free disk space [about 20 MB for JDK 1.1.8, 80 MB for Java 2 SDK], locate the file you downloaded in Step 3 using Windows Explorer, and double-click it. 

This will start up a pretty standard installation program. You don't really have much to decide except for the screen shown below, where you can: 

  • Install to a different path. The default is C:\jdk1.1.8 for the Java 1.1.8 version. If you're going to be installing newer versions as time goes by, then just accept the default. If you think you'll never want more than one version of the JDK on your system at any time, then you may want to shorten this to C:\jdk.

    •  
  • Decide which pieces to install. Normally, the default installation, shown here, is a good choice. If you want to look at the source code for the built-in Java packages, you can install the Java sources which takes another 5 MB.
Select Components dialog when installing JDK 1.1

Other Downloads 

Once the installation is complete, you'll be given an opportunity to view the "Read-Me" file, which you should do. [You may want to print it out as well.] You don't really need to use the configuration instructions, however, because we'll be configuring the JDK using a slightly different technique shortly. 

Before we go on, you may want to download and install the Java documentation. If you normally work online, as I do, this isn't really necessary; but, if you want a local copy, you should go ahead. Go to the same site where you acquired the JDK and look for the "documentation bundle". Once you've downloaded it, install it in the same directory where you've installed the JDK. 

At this point, you're ready to go on to the next step, which is configuring your environment. 

Your Programming Environment 

Windows desktop with Java 2 shortcut icon displayed If you're an old hand at working with command-line tools in an environment like DOS or Unix, then you probably won't have any problem starting up a command prompt, locating the JDK tools, and running the javac compiler or the appletviewer. 

Even for old DOS hands, however, creating a desktop shortcut like that shown here, can free your mind for important things, like writing Java programs.

Here are the steps you need to follow. Read through them first, and then we'll walk you through the process, step-by-step. The instructions will vary a little depending upon whether you are using JDK 1.1 or Java 2, and whether you are using Windows 95/98 or Windows NT. If you are using Windows 2000 or Windows ME, follow the instructions for Windows NT. 

  • Step 1: Create a Shortcut. Right-click on your desktop and choose New|Shortcut from the context menu.

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  • Step 2: Enter Program Name. In Windows 95/98, enter COMMAND.COM. In Windows NT/ME/2K, enter CMD.EXE instead. 

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  • Step 3: Select a Title. Add the title you want to appear on the desktop.

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  • Step 4: Create a Batch File. Create a batch file in the JDK directory. Name it StartJDK118.BAT [W95/98, JDK 1.1.8], or StartJDK13.CMD [NT/2K, Java 2].
  • Step 5: Modify Path and CLASSPATH. Edit batch file to add path to Java command-line tools, and CLASSPATH information.
  • Step 6: Create a subdirectory to hold your files. Use Windows Explorer to create a folder to hold your Java files named C:\JavaProjects.

    •  
  • Step 7: Adjust the Shortcut Properties. Right-click Java shortcut, choose Properties from the popup menu. Select the Shortcut panel, supply directory and path to your batch file.
  • Step 8: Change Your Icon. Click Change Icon and select the Java coffee-cup icon.
  • Step 9: Test Your Installation. Double-click your new shortcut and try it out by typing java at the command prompt. 
Here are the steps in detail. 

Step 1: Create a Shortcut. 

Using a context menu to create a new shortcut on the desktopRight-click on your desktop, and choose New|Shortcut from the context-menu that appears, as you can see here. (In W95, or NT, you won't see the small icons next to Folder and Shortcut like in W98.) 
 
 
 



Step 2: Enter Program Name 

When the Create Shortcut dialog box appears, as you can see below, type cmd in the text field labeled Command line if you are using NT like this: 
Windows NT Shortcut Wizard step 1 [NT]
If you are using Windows 2000 or Windows ME, the Create Shortcut dialog will look like this: 
Specifying a command in Windows 2000 or Windows ME.
If you are using W95/98, then type command instead, as shown below: 
Windows 95/98 Create Shortcut dialog [step 1]
Windows automatically knows you want to run the 32-bit command interpreter, CMD.EXE in Windows NT or 2K, and the MSDOS command interpreter, COMMAND.COM in Windows 95/98. When you're finished, click Next. 

Step 3: Select a Title 

When the "Select a Title for the Program" dialog box appear, type in the name you wish to appear underneath the shortcut on your desktop. In the example shown here, I've just entered Java 1.1, but you may wish to be more specific. 
The Select a Title for the Program dialog box
One of the real advantages of shortcuts is that you can set them up to run different versions of the JDK. You might have one version for the original JDK 1.0, another that runs JDK 1.1, and one that runs SDK 1.3 for the Java 2 Platform. 

Here's what the "Select a Title" dialog looks like with Windows 2K: 

Selecting a shortcut title with Windows 2000.
When you've typed in your name, click Finish. 

Step 4: Create a Batch File 

The instructions that come with the JDK (in the ReadMe file) require you to modify your AUTOEXEC.BAT file or to change the SYSTEM environment. I find it easier to create a batch file to run the JDK so that I can easily switch between different versions. 

To create your batch file, use Windows Explorer to locate your JDK directory. In the example shown here, it is C:\jdk1.3, but if you've installed JDK 1.1, it will probably be C:\jdk1.1.8. Before you actually create your batch file, make sure that the Windows Explorer Folder Options, [accessible from the Windows Explorer Tools menu], are set to "Show all files" and that file extensions are not hidden, like this: (This dialog may look different on your machine.) 

Setting the Windows Explorer Folder Options.

Once you have opened the JDK folder, choose File|New|Text Document from the main Explorer menu. Windows will create a new file in your JDK directory named "New Text Document.txt". Rename the file like this: 

  • For JDK 1.1.8, name the file StartJDK118
  • For J2 SDK 1.3, name the file StartJDK2
  • For Windows 95/98, use the extension .BAT
  • For Windows NT, use the extension .CMD
Windows will complain at you when you attempt to change the file extension, like this: 
Windows Rename warning dialog
Ignore the warning [by clicking the "Yes" button]. At this point, you should see something that looks like this. [The example shown is for Windows 2K and Java 2. Your display may look different. Make sure, however, that the file Icon is a small gear, and not the default Text file Icon.] 
Creating the StartJava batch file.
Once you've created your batch file, simply right-click it and choose Edit (not Open) from the popup menu that appears. Now you're ready for the next step. 

Step 5: Modify Your Path and Classpath 

When you edit you batch file, Windows will open up Notepad. You'll need to add lines to modify the PATH, the CLASSPATH, and, in the case of Windows 95/98, run the DOSKEY utility as well. 

Windows NT/2K and Java 2 

Here is what your file should look like for Windows NT and Java 2: 
Java batch file for Windows NT and the Java 2 SDK
As you can see, the file contains two lines: 
PATH=C:\jdk1.3\bin;%PATH%
SET CLASSPATH=.;C:\jdk1.3\jre\lib\rt.jar
The first line places the Java 2 command-line tools directory in front of any existing PATH that may exist. The second line gives your programs access to the Java 2 runtime library, contained in the file rt.jar.

Windows 95/98 and JDK 1.1 

Here is what your file should look like for Windows 95/98 and Java 1.1: 
JDK 1.1 batch file to set the PATH and CLASSPATH on Windows 95/98
As with the Windows NT version, this also contains two lines: 
PATH=C:\jdk1.1.8\bin;%PATH%
SET CLASSPATH=.;C:\jdk1.1.8\lib\classes.zip
The biggest difference between the two is that the Java runtime library is contained in a file named classes.zip, located in the C:\jdk\lib directory. Under Java 2, the runtime library is located in the file rt.jar, located in the C:\jdk\jre\lib directory. 

If you are using Windows 95/98 [but not NT] you'll also want to add one more line to your batch file: 

DOSKEY /INSERT
The side-bar explains why adding DOSKEY is a good idea. In Windows NT/2K, the functionality of DOSKEY is built into the 32-bit command interpreter, CMD.EXE. 
 
What is DOSKEY?
Because you will be repeating the Edit-Compile-Test cycle more times than you'd like, DOSKEY allows you to repeat a previous command-line incantation simply by using the arrow keys to recycle them. Pressing up-arrow brings back the previous commands, one-by-one. DOSKEY also allows you to edit your commands before pressing ENTER.

You may also want to start up your programmer's text editor, whenever you start the JDK. The batch file is a great place to do that. For instance, to start the Scintilla Text Editor whenever you launch your JDK: 

  • Download the executable file Sc1.exe and save it in your JDK bin directory.(That's the directory that contains the file JAVA.EXE.)
  • Add one more line to the end of the batch file containing the single word: SC1
Now, when you launch your JDK, the SciTE text editor will automatically start up, and you'll be able to compile your Java programs from within the editor. 

Step 6: Create a Working Directory 

Creating the JavaProjects directory in Windows ExplorerCreate a folder to save your Java programs. 

Using Windows Explorer, select New|Folder from the main menu, and make a directory called C:\JavaProjects, [or some other name if you prefer], as you can see here: 
 


Step 7: Setup the Shortcut Environment 

Selecting Properties to modify JDK shortcut on desktopWhen Windows creates the shortcut for you, as you can see in the figure here, it automatically uses the MS-DOS icon, and also uses your default MS-DOS environment. We want to change both of those. 

Right-click on your new shortcut and you should see a context menu similar to that shown here. If, instead, you see another menu, make sure that the shortcut icon is highlighted, as it appears in the figure. From the context menu, choose Properties. 


Windows 95/98 and JDK 1.1 

Windows 95/98 and Windows NT/2K have different shortcut property sheets. We'll look at Windows 95/98 first. Choose the second tab, titled "Program" and change the fields as shown here: 
Setting the Properties dialog for JDK 1.1

Change the text in the "Working" text field so that it refers to the directory you created in Step 6. Change the value in the "Batch file" text field to: 

C:\jdk1.1.8\StartJDK118.BAT
(As before, this assumes you have installed the JDK into the C:\jdk1.1.8 directory. If you've installed it somewhere else, or if you are using Java 2, change this to reflect the actual name and location of the batch file you've created.) 

Windows NT or 2K and Java 2 

In Windows NT, the second tab is titled "Shortcut" instead of "Program". Note that there is no field to enter a batch file name. Instead, replace the contents of the Target field with: 
\system32\CMD.EXE /K C:\jdk1.3\StartJDK13.CMD
There are three parts to this: 
 
\system32\CMD.EXE run the 32-bit command interpreter
/K remain in memory
C:\jdk1.3\StartJDK13.CMD the batch file to start with

In the "Start in" text field, add C:\JavaProjects, just as you did with 95/98. The finished Java Properties dialog should look like this: 

Setting the Properties dialog for Windows NT and Java 2

Windows 2000 and Windows ME are very similar to the Windows NT procedures, but the Dialog box looks slightly different, as you can see: 

The shortcut properties dialog in Windows 2000.
Before we get around to testing your installation, let's take care of some more pressing needs. Let's fix the icon so that you can tell you're working with Java! Do that by clicking Change Icon button on the property sheet, and then going to the next step. 

[In Windows NT, this may bring up a misleading warning, similar to that shown here. You can safely ignore this.] 

Change Icon warning message

Step 8: Change Your Icon 

When you click Change Icon, Windows shows you a list of icons that it has available. You aren't limited to the icons that Windows supplies, however. Instead, click Browse, and navigate to the jdk1.1.8\bin directory (as shown in the figure here), and select the file named winawt.dll: 
 
Locating the Java icon for JDK 1.1 The winawt.dll file

For Java 2, navigate to the C:\jdk1.3\jre\bin directory as shown here, and locate the file named awt.dll. 
 
Locating the Java icon in Java 2 The awt.dll file

If you cannot find either file, make sure that Windows is showing you all files by changing the Folder Options to "Show all files" as mentioned earlier. 

Step 9: Test Your Installation 

Double-click your new shortcut and you should see a command window similar to that shown in the first three lines below. At the command prompt, type javac and press ENTER. If you've set up everything correctly, you'll see a list of the  JAVAC.EXE compiler options as shown in the bottom of your screen. 
Testing your JDK shortcut.
If, instead, you see an error message that says "Bad Command or File Name", that means you've misstyped the path to the Java executable. Reedit your batch file, and try again. 

Using the JDK 

Learning is a process that involves reading, and understanding, and doing as well. In programming, there's nothing quite so helpful as trying out an example to make sure you really understand. The easiest way to learn to use the JDK is to create both a Java applet and an application, using the JDK development tools. 

Creating Your Source Code 

Now that the JDK is configured, let's use it to create your source-code files. Double-click your new shortcut, type EDIT, under Windows 95/98, or Notepad, under Windows NT, and then type and save each of the programs listed below. (If you installed the SciTE text editor, you don't need to start up EDIT or Notepad.) 
  1. Put each listing into a separate file. Do not put them together into one file.

    2.  
  2. Make sure you name each file correctly: FirstApplet.java, FirstApp.java, and FJA.html. The case of each filename is significant. [If you are using Notepad, make sure you don't inadvertently end up with files named FirstApplet.java.txt. If that happens, place the entire filename inside quotes when saving the file.]

    3.  
  3. Make sure you carefully check the spelling of each word in each file. Like the filenames, the case of each word is significant in a Java program. The words main and Main, for instance, are two different things.

    4.  
  4. Save all three files in your JavaProjects directory.

Listing 1: FirstApplet.java 

import java.awt.*;
import java.applet.*;
public class FirstApplet extends Applet
{
   Label theLabel;
   public void init()
   {
     theLabel = new Label("Hi Mom! Your child, Applet");
     add(theLabel);
   }
}

Listing 2: FJA.html 

<html><head><title>First Applet</title></head>
<body>
<applet code=FirstApplet width=300 height=200>
</applet>
</body>
</html>

Listing 3: FirstApp.java 

public class FirstApp
{
   public static void main(String[] args)
   {
      System.out.println("Hi Mom! - Your child, App");
   }
}

Compiling Your Code 

Once you've created your source-code files, the next step is to compile your programs, producing Java byte-code. To compile your programs, return to the command prompt and type in the following: 
C:>\JavaProjects\> javac FirstApp.java
C:>\JavaProjects\> javac FirstApplet.java
If there are no problems, you will simply be returned to the command prompt. Following are some problems you may encounter, along with their solutions: 
  • Misspelling the name of the source code file. If you ask the compiler to compile FistApplet.java instead of FirstApplet.java, you'll see a message like this:
      • C:\JavaProjects\> javac FistApplet.java
      error: Can't read: FistApplet.java

      1 error
       

    • Being careless with your capitalization or spelling when entering your source code. If, inside your source code, you name your class FIRSTAPPLET instead of FirstApplet, you'll see a message like this:
      C:\JavaProjects\> javac FirstApplet.java
      FirstApplet.java:4: Public class FIRSTAPPLET must be defined in a file called "FIRSTAPPLET.java".
      public class FIRSTAPPLET extends JApplet
      ^

      1 error

    • Adding or forgetting punctuation. Remember, your very literal computer only pretends to be intelligent. It gets completely lost when you fail to spell everything out exactly. For instance, if you inadvertently use a parentheses ( instead of a brace { when typing in your listing, the compiler will tell you this:
      C:\JavaProjects\> javac FirstApplet.java
      FirstApplet.java:9: '{' expected.
      public void init()
      ^
      1 error
    Notice that the compiler does its best to point to your the program and line number where it gets lost. As you learn more about Java's syntax, you'll find these messages more helpful. 

    Run Your Code 

    Once you've successfully compiled your programs, it's time to try them out. Follow these instructions: 

    In your DOS command window, run your applet by typing: 

    C:\JavaProjects\> appletviewer FJA.html
    This should start the appletviewer application, which will launch a separate window, and display your message inside it.Here's what the FirstApplet Java applet looks like as it runs: 
    Running the FirstApplet Java applet in appletviewer

    Close the appletviewer window, using either the closing control in the upper-right corner of the appletviewer window, or by simply pressing <CTRL>-<C> from the DOS window that launched the appletviewer. 

    Return to the DOS command window and run your application by typing: 

    C:\JavaProjects\> java FirstApp
    The Java interpreter should run your program and display its output in the same window. 
    Here's what your the FirstApp Java application looks like as it runs: 
    Running the FirstApp Java program
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