ch1.htm

Java_by_Example,初级经典例子哦,珍藏版本

version 1.0.1 has been used for many of the test applets, version

1.0.2 represents Sun's latest installment of the JDK at the time

of this book's completion. However, because the language is constantly

being refined (and was only recently released for  Windows), there

may have been a newer version released since this book was written.

<P>

If you'd like to be sure you have the latest version, you can

find HotJava and the JDK on the Sun Microsystems site, located

at <TT><A TARGET="resource window" HREF="http://www.sun.com">http://www.sun.com</A></TT>. Once you connect up to Sun Microsystems'

home page, navigate to the page shown in Figure 1.5, which provides

access to tons of information about Java and enables you to download

the files you need. (Of course, Web pages constantly change. Sun

Microsystem's site may have changed significantly by the time

you read this.)

<P>

<A HREF="f1-5.gif"><B> Figure 1.5 : </B><I>You can download HotJava and the Java Development Kit from Sun Microsystems' Web pages.



</I></A><P>

<P>

If you want to try out a copy of Netscape Navigator 2.0, hop onto

the ol' WWW and go to <TT><A TARGET="resource window" HREF="http://www.netscape.com">http://www.netscape.com</A></TT>, which

is Netscape's home page. From there, you can find your way to

the page shown in Figure 1.6. From this page, you can download

any of the software that Netscape has up on the Web.

<P>

<A HREF="f1-6.gif"><B> Figure 1.6 : </B><I>You can get Netscape Navigator 2.0 <r>from Netscape's WWW site.



</I></A><P>

<P>

<CENTER>

<TABLE BORDER=1 WIDTH=80%>

<TR VALIGN=TOP><TD><B>NOTE</B></TD></TR>

<TR VALIGN=TOP><TD>

<BLOCKQUOTE>

You might also want to find your way to <TT><A TARGET="resource window" HREF="http://www.microsoft.com">http://www.microsoft.com</A></TT>, where you can find information about Microsoft's new Web browser, Internet Explorer 3, which features Java support.

</BLOCKQUOTE>



</TD></TR>

</TABLE>

</CENTER>

<P>

<H2><A NAME="ExampleInstallingHotJava"><FONT SIZE=5 COLOR=#Ff0000>

Example: Installing HotJava</FONT></A></H2>

<P>

The HotJava browser is contained in a self-extracting compressed

file, which you may download from Sun's Web site at <A TARGET="resource window" HREF="http://java.sun.com">http://java.sun.com</A>.

After you extract HotJava's many files (there's a ton of them!)

by double-clicking the file, the extraction program uncompresses

the files and stores them in a folder named HOTJAVA.  Once the

files are extracted, you can copy the folder anywhere you like

on your hard disk.

<P>

When you examine the HOTJAVA folder, you'll see the directory

structure shown in Figure 1.7. The BIN folder contains the main

HotJava application (HOTJAVA.EXE), as well as many of the Java

environment's tools, including the compiler, interpreter, and

profiler.  The LIB folder contains a number of other files needed

for HotJava:

<P>

<A HREF="f1-7.gif"><B> Figure 1.7 : </B><I>After extraction, the HOTJAVA directory will contain all of HotJava's files.



</I></A><P>

<P>

<CENTER>

<TABLE BORDER=1 WIDTH=80%>

<TR VALIGN=TOP><TD WIDTH=163><BLOCKQUOTE>

lib/classes.zip.</BLOCKQUOTE>



</TD><TD WIDTH=300><BLOCKQUOTE>

This file is needed by the compiler and interpreter, so do not unzip it.</BLOCKQUOTE>



</TD></TR>

<TR VALIGN=TOP><TD WIDTH=163><BLOCKQUOTE>

lib/properties/.</BLOCKQUOTE>



</TD><TD WIDTH=300><BLOCKQUOTE>

This is the template and system defaults for the HotJava properties file. </BLOCKQUOTE>



</TD></TR>

<TR VALIGN=TOP><TD WIDTH=163><BLOCKQUOTE>

lib/hotjava/ and<BR>

lib/templates/.</BLOCKQUOTE>



</TD><TD WIDTH=300><BLOCKQUOTE>

These are customizable textual elements and HTML.</BLOCKQUOTE>



</TD></TR>

</TABLE>

</CENTER>

<P>

<P>

<CENTER>

<TABLE BORDER=1 WIDTH=80%>

<TR VALIGN=TOP><TD><B>NOTE</B></TD></TR>

<TR VALIGN=TOP><TD>

<BLOCKQUOTE>

Documentation for HotJava must be accessed online from the program's Help menu.</BLOCKQUOTE>



</TD></TR>

</TABLE>

</CENTER>

<P>

<H2><A NAME="ExampleInstallingtheJDK"><FONT SIZE=5 COLOR=#Ff0000>

Example: Installing the JDK</FONT></A></H2>

<P>

Although the compressed HotJava file contains many of the Java

environment's programs such as the compiler and the interpreter,

the Java Developer's Kit contains the complete development suite,

including some files not packaged with HotJava. For example, the

HotJava compressed file doesn't include the Java debugger or the

Appletviewer application, which enables you to view applets without

having to load them into a Web browser. The JDK also comes packaged

with over 20 sample applets. More importantly, the JDK contains

the most up-to-date documentation and tools.

<P>

You can find the JDK on this book's CD-ROM, in the JDK folder,

or you can download the latest version of the JDK from the Sun

Microsystems Web site. On the CD-ROM, the compressed file that

contains the JDK is called JDK.EXE. After copying the file to

your hard disk (or after downloading the JDK from Sun), you install

it in exactly the same way you installed the HotJava browser.

That is, you double-click the self-extracting compressed file.

<P>

When the files have been extracted (it might take a while), you

can move the resultant JAVA folder anywhere you like on your hard

disk, although you'll probably want it on the disk's root directory,

which is where this book's forthcoming examples will assume it's

located. Figure 1.8 shows the contents of the JAVA folder (at

least, the contents at the time of this writing; the development

kit may have been revised by the time you read this).

<P>

<A HREF="f1-8.gif"><B> Figure 1.8 : </B><I>The Java Developer's Kit will be in the JAVA folder after you extract its compressed files.



</I></A><P>

<P>

If you examine the folders that make up the JDK, you'll see that

the BIN folder holds the developer tools, such as the compiler,

the interpreter, the debugger, and the profiler. The DEMO folder

contains the many example applets that you can examine to learn

more about the Java language and how it's used. In your JAVA folder,

you'll also find a file called SRC.ZIP. This compressed file contains

the source code for the classes included with the JDK.

<H2><A NAME="Summary"><FONT SIZE=5 COLOR=#Ff0000>

Summary</FONT></A></H2>

<P>

Java just may be the biggest thing to hit the World Wide Web since,

well, the Web itself. As you'll see in the forthcoming chapters,

Java not only provides a way to create secure applications that

can be used safely on the Internet, but the language also represents

a complete shift in the way people may think about their computers

in the future. Because a Java applet can be located anywhere on

the Web yet still be executable on your computer, your computer's

storage may well expand from its tiny hard drive to include all

of the Internet. As Java becomes more refined, and as more people

like yourself start writing Java applets and applications, the

cyber world that is the Internet may never be the same.

<H2><A NAME="ReviewQuestions"><FONT SIZE=5 COLOR=#Ff0000>

Review Questions</FONT></A></H2>

<OL>

<LI>Give three reasons why Java is so suitable for Web applications.

<LI>What's the difference between a Java applet and a Java stand-alone

application?

<LI>Why are Java applets considered to be platform neutral?

<LI>How does an Applet work within an HTML document?

<LI>What are the two benefits of Java that make it an Internet-saavy

language?

</OL>

<H2><A NAME="ReviewExercises"><FONT SIZE=5 COLOR=#Ff0000>

Review Exercises</FONT></A></H2>

<OL>

<LI>Explore the many resources available to Java programmers on

the Java WWW pages, located at <TT>http:/www.netscape.com</TT>.

(Remember that some commerical online services, such as America

Online, give you access to the World Wide Web.)

<LI>Explore Netscape's Web pages, located at <TT>http:/www.netscape.com</TT>.

<LI>If you've downloaded a copy of Netscape Navigator 2.0, install

it on your system.

<LI>Using the HotJava or Netscape browser, do a Webcrawler search

(<TT>www.webcrawler.com</TT>) using the keywords &quot;java&quot;

or &quot;java applet.&quot; Locate Applets others have written,

follow the links and load them into your browser

</OL>

<HR>



<CENTER><P>







<HR WIDTH="100%"></P></CENTER>

<!-- reference library footer #1-->
</CENTER>
<IMG SRC="/images/rule.gif" WIDTH="460" HEIGHT="5" VSPACE="5"
ALT="Ruler image"><br>

<FONT SIZE="-1">

Contact <a href="mailto:[e-mail]">
[e-mail]</a> with questions or comments.<br>


<a href="/legal/">
Copyright 1998</a> 
<a href="http://www.earthweb.com" target="_top">
EarthWeb Inc.</a>,  All rights reserved.<BR>
PLEASE READ THE <a href="/reference/usage.html">ACCEPTABLE USAGE STATEMENT</a>.
<BR>
Copyright 1998 Macmillan Computer Publishing. All rights reserved.
</FONT>
</BLOCKQUOTE>


<!--outer table--><TD VALIGN="TOP">

<!--right side ads -->
<a target="resource window" href="http://adserver.developer.com/cgi-bin/accipiter/adclick.exe/AREA=DCAD1.REF" alt="Click here for more info"><img src="http://adserver.developer.com/cgi-bin/accipiter/adserver.exe/AREA=DCAD1.REF" alt="Click here for more info" height="88" width="88" border="0"></a>
<P>
<a target="resource window" href="http://adserver.developer.com/cgi-bin/accipiter/adclick.exe/AREA=DCAD2.REF" alt="Click here for more info"><img src="http://adserver.developer.com/cgi-bin/accipiter/adserver.exe/AREA=DCAD2.REF" alt="Click here for more info" height="88" width="88" border="0"></a>
<P>



</td>
</tr>
</table>
</BODY>
</HTML>