Getting to know your Java programming environment

Expected duration: 60 minutes

Exercise 0:  Install Java SE and NetBeans IDE

(0.1) Download and install JDK 6 on you computer

1.  Download JDK 6

• From your browser, go to download page of the Java SE.
• Observe that there are multiple choices. 
• You can choose any of these but for the sake of this exercise, choose JDK 6 Update x as show in in Figure-0.10 below.  (The latest version as of August 10th, 2008 is version 7.)
  

Figure-0.10: Choose JDK 6 Update x

• Select the Platform of your choice from the drop-down menu.
• Check the checkbox of  "I agree to the Java SE Development Kit 6 License Agreement".
• Click Continue.
  

• Choose OS platform specific off-line installation, Windows Offline Installation for the Windows platform, for example.
• Click the link of jdk-6u6-windows-i586-p.exe (or click Download Selected with Sun Download Manager.)
  

Figure-0.11: Choose the file

2. Install JDK 6

• Double-click jdk-6u6-windows-i586-p.exe  (for Windows) to run the installation. (Other platforms, of course, has different names.)
  
• Observe that the installation gets started.
• When License agreement dialog box is displayed, click I accept the terms in the license agreement. (Figure-0.12 below)
  
• Click Next.

Figure-0.12: License Agreement

• Observe that J2SE Development Kit 5.0 Update x - Custom Setup dialog box appears.
• If you want to install it in a different location, click Change and specify the directory of your choice.
  
• Click Next. (Figure-0.13 below)
  

Figure-0.13: Specify the installation location

• Observe that the installation process of the J2SE Development Kit gets underway for a minute or two.
• Observe that J2SE Runtime Environment 5.0 Update x - Custom Setup dialog box appears. (Figure-0.14 below)
  
• Click Next. (Figure-0.14 below)

Figure-0.14: Custom Setup of the J2SE Runtime Environment

• Observe that Browser Registration dialog box appears.
• Click Next.  (Figure-0.15 below)
  

Figure-0.15: Browser registration

• Observe that the installation process of the J2SE Runtime Environment gets underway.
  
• Observe that Installation Completed screen appears.
  

(0.2) Download and install NetBeans IDE on your computer

1. From your browser, go to download page of the NetBeans IDE 6.1.
2. Select OS specific version of the NetBeans IDE from the drop-down menu.
3. Download and install either Web & Java EE or Java SE (if you have a limited disk space).


Figure-1.11: Download NetBeans IDE 6.1

Exercise 1: Write, compile, and run Hello Java program using command line tool

The goal of this exercise is to let you experience a complete development cycle  - writing, compiling, and running a simplest possible Java program - using command line tools.  If you have done any programming in the past using different programming languages such as C or C++, this is not that much different from it. (There is a slight difference, however.  In Java, the compiler which is called javac compiles the Java source code into what is called bytecode which can be run on any Java compliant platform, thus provides the portability of the Java programs. The bytecode is the same thing as Java class file, which is represented by *.class file notation.)

1. Build and run Hello Java program using "javac" and "java" command
   
2. Experiment with "javac" compiler
   
3. Experiment with "java" command

(1.1) Build and run Hello Java program using "javac" compiler and "java"

1. Create a directory where you are going to write Java programs

2. Write Hello.java using your editor of choice such as notepad on Windows platform or gedit on Solaris platform (in this example, I am using jedit) as shown in Code-1.10 below.  You can cut and paste the code from the Code-1.10 but I encourage you to write the code line by line yourself manually just to experience some compile errors.

C:\myjavaprograms>jedit Hello.java

public class Hello {         /**      * My first Java program      */     public static void main( String[] args ){                 // Print the string "Hello world" on screen         System.out.println("Hello world");             } }

Code-1.10: Hello.java

3. Compile Hello.java using javac compiler.  The javac compiler comes with J2SE SDK you've download.  It resides in %JAVA_HOME%\bin (Windows) or $JAVA_HOME/bin (Solaris/Linux) directory. The result of compilation will be the creation of Hello.class file.

C:\myjavaprograms>javac Hello.java

---

Trouble-shooting #1: If you experience the following error condition, it means the %JAVA_HOME%\bin for Windows platform or $JAVA_HOME/bin for Solaris/Linux platform is not set in your path.  You can try C:\Program Files\Java\jdk1.6.0_06\bin\javac Hello.java (for Windows) if you want to proceed without setting the path.

C:\myjavaprograms>javac Hello.java
      'javac' is not recognized as an internal or external command, operable program or batch file

Solution #a: Add C:\"Program Files"\Java\jdk1.5.0_10\bin (for Windows platform) or /usr/opt/jdk1.5.0_10/bin (for Solaris/Linux platform) to the path environment variable.

Solution #b: You can specify the full path as following:

C:\myjavaprograms>C:\"Program Files"\Java\jdk1.5.0_10\bin\javac Hello.java

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4. Make sure Hello.class file has been created.  The Hello.class file contains bytecode representation of the Hello class.

C:\myjavaprograms>dir Hello.class
 Volume in drive C is ACER
 Volume Serial Number is 58CE-B0DC

 Directory of C:\myjavaprograms

01/19/2007  12:16 AM               415 Hello.class
               1 File(s)            415 bytes
               0 Dir(s)  21,578,907,648 bytes free

6. Run the Hello program using java command. The java command starts the Java Virtual Machine and runs the Hello program in this example.  A Java program can be made of multiple Java classes and and a set of libraries.  In this example, the Hello program just contains a single class called Hello.class. You can regard the java command as Java interpreter.

C:\myjavaprograms>java Hello
Hello world

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Trouble-shooting #2: If you experience the following error condition, it is highly likely you compiled the program with JDK 1.4 and then run it with JDK 6.

C:\myjavaprograms>java Hello
Exception in thread "main" java.lang.UnsupportedClassVersionError: Hello (Unsupported major.minor version 49.0)

Solution: Add C:\"Program Files"\Java\jdk1.5.0_10\bin (for Windows platform) or /usr/opt/jdk1.5.0_10/bin (for Solaris/Linux platform) to the front of the path environment variable.

Trouble-shooting #3: If you experience the following error condition, it is highly likely because your have set CLASSPATH enviroment variable set without the current directory.

C:\myjavaprograms>java Hello
Exception in thread "main" java.lang.NoClassDefFoundError: Hello

Solution: Try "java -classpath . Hello" (There is a dot . after -classpath) as following. We will learn about classpath later on.

C:\myjavaprograms>java -classpath . Hello
This is my first Java program!

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7. Modify Hello.java as shown in Code-1.11 below.  The code fragment that needs to be changed are highlighted in bold and blue-colored font.

public class Hello {         /**      * My first Java program      */     public static void main( String[] args ){                 // Print the string "Hello world" on screen         System.out.println("This is my first Java program!");             } }

Code-1.11: Modified Hello.java

8. Compile and run the program. Observe that new message is displayed.

C:\myjavaprograms>javac Hello.java

C:\myjavaprograms>java Hello
This is my first Java program!

                                                                                                                        return to top of the exercise

(1.2) Experiment with "javac" compiler

In this step, you are going to learn how to use various command line options of the javac compiler.

1. Display the usage information of the javac compiler by using -help option

2. Run the javac compiler with -verbose option

C:\myjavaprograms>javac -verbose Hello.java
[parsing started Hello.java]
[parsing completed 516ms]
[search path for source files: [.]]
[search path for class files: [C:\Program Files\Java\jdk1.6.0_06\jre\lib\rt.jar,C:\Program Files\Java\jdk1.6.0_06\jre\lib\jsse.jar, C:\Program Files\Java\jdk1.6.0_06\jre\lib\jce.jar, C:\Program Files\Java\jdk1.6.0_06\jre\lib\charsets.jar,C:\Program Files\Java\jdk1.6.0_06\jre\lib\ext\dnsns.jar, C:\Program Files\Java\jdk1.6.0_06\jre\lib\ext\localedata.jar, C:\Program Files\Java\jdk1.6.0_06\jre\lib\ext\sunjce_provider.jar, C:\Program Files\Java\jdk1.6.0_06\jre\lib\ext\sunpkcs11.jar, .]]
[loading C:\Program Files\Java\jdk1.6.0_06\jre\lib\rt.jar(java/lang/Object.class)]
[loading C:\Program Files\Java\jdk1.6.0_06\jre\lib\rt.jar(java/lang/String.class)]
[checking Hello]
[loading C:\Program Files\Java\jdk1.6.0_06\jre\lib\rt.jar(java/lang/System.class)]
[loading C:\Program Files\Java\jdk1.6.0_06\jre\lib\rt.jar(java/io/PrintStream.class)]
[loading C:\Program Files\Java\jdk1.6.0_06\jre\lib\rt.jar(java/io/FilterOutputStream.class)]
[loading C:\Program Files\Java\jdk1.6.0_06\jre\lib\rt.jar(java/io/OutputStream.class)]
[wrote Hello.class]
[total 1141ms]

(1.3) Experiment with "java" command

In this step, hyou are going to learn how to use various command line options of the java command.  You can think of java command as Java Virtual machine.

1. Display the usage information of the java command with -help option or -? option.

C:\myjavaprograms>java -help
Usage: java [-options] class [args...]
           (to execute a class)
   or  java [-options] -jar jarfile [args...]
           (to execute a jar file)

where options include:
    -client       to select the "client" VM
    -server       to select the "server" VM
    -hotspot      is a synonym for the "client" VM  [deprecated]
                  The default VM is client.

    -cp <class search path of directories and zip/jar files>
    -classpath <class search path of directories and zip/jar files>
                  A ; separated list of directories, JAR archives,
                  and ZIP archives to search for class files.
    -D<name>=<value>
                  set a system property
    -verbose[:class|gc|jni]
                  enable verbose output
    -version      print product version and exit
    -version:<value>
                  require the specified version to run
    -showversion  print product version and continue
    -jre-restrict-search | -jre-no-restrict-search
                  include/exclude user private JREs in the version search
    -? -help      print this help message
    -X            print help on non-standard options
    -ea[:<packagename>...|:<classname>]
    -enableassertions[:<packagename>...|:<classname>]
                  enable assertions
    -da[:<packagename>...|:<classname>]
    -disableassertions[:<packagename>...|:<classname>]
                  disable assertions
    -esa | -enablesystemassertions
                  enable system assertions
    -dsa | -disablesystemassertions
                  disable system assertions
    -agentlib:<libname>[=<options>]
                  load native agent library <libname>, e.g. -agentlib:hprof
                    see also, -agentlib:jdwp=help and -agentlib:hprof=help
    -agentpath:<pathname>[=<options>]
                  load native agent library by full pathname
    -javaagent:<jarpath>[=<options>]
                  load Java programming language agent, see java.lang.instrument

2. Run the java command with -verbose option

Summary

In this exercise, you have built and run a simple Hello Java program using javac compiler and java command.  You have learned some of the options of the javac compiler and java command.
   
                                                                                                                                   Return to the top

Exercise 2: Write, compile, and run Hello Java program using NetBeans IDE

In this exercise, you are going to build the same application you built in the Exercise 1 above using NetBeans IDE.

1. Start NetBeand IDE
   
2. Create a NetBeans project
3. Build and run the program
   

(2.1) Start NetBeans IDE

1. Double-click NetBeans IDE Icon on the desktop to start the NetBeans IDE. Observe the NetBeans IDE gets started.  (Figure-2.10 below)

Figure-2.10: NetBeans IDE

(2.2) Create a NetBeans project

1. Select File from top-level menu and select New Project.  (Figure-2.20 below) 

Figure-2.20: Create New Project

2. Observe that the New Project dialog box appears.
3. Select Java under Categories section and Java Application under Projects section. (Figure-2.21 below)
4. Click Next.

Figure-2.21: Create Java Application project

5. Under Name and Location pane, for the Project Name field, enter MyHelloProject.
6. For the Create Main Class field, enter Hello.  (Figure-2.22 below)
7. Click Finish. 

Figure-2.22: Give a project name

8. Observe that the MyHelloProject node is created under Projects pane of the NetBeans IDE.
9. Modify the Hello.java as shown in Figure-2.23 below.

Figure-2.23: Modified Hello.java

10. Introduce a syntax error in the program and observe that NetBeans IDE immediately highlights the problem as shown in Figure-2.24 below.  It detects that the keyword void is misspelled as voidx.

Figure-2.24: NetBeans IDE detects a syntax error (compile error)

11. Remove the syntax error.

(2.3) Build and run the program

1. Right click MyHelloProject and select Run. (Figure-2.30 below)

Figure-2.30: Build and run the project

2. Observe that the Hello.java is compiled and then run.  (Figure-2.31 below)

Figure-2.31: Result of running the MyHelloProject

Summary

In this exercise,  you have built and run Hello Java application using NetBeans IDE.

                                                                                                                        return to the top

Homework exercise (for people who are taking Sang Shin's "Java Programming online course")

• Hello, this is the first line from MyHelloProject2.
• This is the second line from the same project.
  

• Zip file of the the MyHelloProject2 NetBeans project.  (Someone else should be able to open and run it as a NetBeans project.)  You can use your favorite zip utility or you can use "jar" utility that comes with JDK as following.
  
• cd <parent directory that contains MyHelloProject2 directory> (assuming you named your project as MyHelloProject2)
  
• jar cvf MyHelloProject2.zip MyHelloProject2 (MyHelloProject2 should contain nbproject directory)
• Captured output screen  - name it as JavaIntro-javaprogenv.gif orJavaIntro-javaprogenv.jpg (or JavaIntro-javaprogenv.<whatver graphics format>)
• Any screen capture that shows that your program is working is good enough.  No cosmetic polishment is required.
• Under Windows, you can do the screen capture by taking steps below
• Press Alt+PrtSc key combination to copy the current window image to the clipboard
• Select Start / All Programs / Accessories / Paint
• Ctrl+V to paste into Paint
• File / New, then Ctrl+V
• File / Save As - pull down "Save As Type" to be GIF or JPG, then save
• Under Solaris/Linux, you can take one of the following two approaches
• Option 1: Type "import HWExercise3.2.jpg" in a terminal window and then you can select the area of the screen that you want with the mouse.
• Option 2: Use gimp program.  It has screen capture functionality.
• If you decide to use different IDE other than NetBeans, the zip file should contain all the files that are needed for rebuilding the project - war file with necessary source files is OK.