compile.html

java 基础的 一点东西,,可以看看

Here is the <A HREF="./Code/ExampleProgram.java">ExampleProgram.java</A>
source code file if you do not want to type the program text in yourself.

<A NAME="comp"></A>
<H3>Compiling the Program</H3>

A program has to be converted to a form the Java VM can understand
so any computer with a Java VM can interpret and run the program. 
Compiling a Java program means taking the programmer-readable text in your 
program file (also called source code) and converting it to bytecodes, 
which are platform-independent instructions for the Java VM.

<P>
The Java compiler is invoked at the command line on 
Unix and DOS shell operating systems as follows:

</FONT>

<PRE>
  javac ExampleProgram.java
</PRE>

<FONT FACE="Verdana, Arial, Helvetica, sans-serif">

<BLOCKQUOTE>
<HR>
<STRONG>Note:</STRONG>
Part of the configuration process for setting up the Java platform
is setting the class path. The class path can be set using either
the <CODE>-classpath</CODE> option with the <CODE>javac</CODE>
compiler command and <CODE>java</CODE> interpreter command,
or by setting the <CODE>CLASSPATH</CODE> environment variable. You 
need to set the class path to point to the directory where the
<CODE>ExampleProgram</CODE> class is so the compiler and 
interpreter commands can find it. See
<A HREF="http://java.sun.com/products/jdk/1.2/docs/tooldocs/tools.html">Java 2
SDK Tools</A> for more information. 
<HR>
</BLOCKQUOTE>

<A NAME="run"></A>
<H3>Interpreting and Running the Program</H3>

Once your program successfully compiles into Java bytecodes, you can 
interpret and run applications on any Java VM, or interpret and
run applets in any Web browser with a Java VM built in such as
Netscape or Internet Explorer. Interpreting and running
a Java program means invoking the Java VM byte code interpreter, 
which converts the Java byte codes to platform-dependent machine 
codes so your computer can understand and run the program.

<P>
The Java interpreter is invoked at the command line on 
Unix and DOS shell operating systems as follows:

</FONT>

<PRE>
  java ExampleProgram
</PRE>

<FONT FACE="Verdana, Arial, Helvetica, sans-serif">

At the command line, you should see:

</FONT>

<PRE>
  I'm a Simple Program
</PRE>

<FONT FACE="Verdana, Arial, Helvetica, sans-serif">

Here is how the entire sequence looks in a terminal window:

<P>
<IMG SRC="./Art/examprog.gif" WIDTH="196" HEIGHT="106" ALT="">
<P>

<A NAME="debug"></A>
<H3>Common Compiler and Interpreter Problems</H3>

If you have trouble compiling or running the simple example
in this lesson, refer to the 
<A HREF="http://java.sun.com/docs/books/tutorial/getStarted/problems/index.html">Common Compiler and Interpreter Problems</A> lesson in   
<A HREF="http://java.sun.com/docs/books/tutorial/trailmap.html">The Java Tutorial</A> for troubleshooting help.

<A NAME="comm"></A>
<H3>Code Comments</H3>

Code comments are placed in source files to describe
what is happening in the code to someone who might be
reading the file, to comment-out lines of code to isolate
the source of a problem for debugging purposes, or to generate
API documentation. To these ends, the Java language supports three
kinds of comments: double slashes, C-style, and doc comments.

<H4>Double Slashes</H4>

Double slashes (<code>//</code>) are used in the C++ programming
language, and tell the compiler to
treat everything from the slashes to the end of the line as
text.

</FONT>

<PRE>
//A Very Simple Example
class ExampleProgram {
  public static void main(String[] args){
    System.out.println(&quot;I'm a Simple Program&quot;);
  }
}
</PRE>

<FONT FACE="Verdana, Arial, Helvetica, sans-serif">

<H4>C-Style Comments</H4>

Instead of double slashes, you can use C-style
comments (<code>/* */</code>) to enclose one or
more lines of code to be treated as text.

</FONT>

<PRE>
/* These are
C-style comments
*/
class ExampleProgram {
  public static void main(String[] args){
    System.out.println(&quot;I'm a Simple Program&quot;);
  }
}
</PRE>

<FONT FACE="Verdana, Arial, Helvetica, sans-serif">

<H4>Doc Comments</H4>

To generate documentation for your program, use the doc comments
(<code>/** */</code>) to enclose lines of text for the
<code>javadoc</code> tool to find. The <code>javadoc</code> tool
locates the doc comments embedded
in source files and uses those comments to generate API  documentation.

</FONT>

<PRE>
/** This class displays a text string at
*  the console.
*/
class ExampleProgram {
  public static void main(String[] args){
    System.out.println(&quot;I'm a Simple Program&quot;);
  }
}
</PRE>

<FONT FACE="Verdana, Arial, Helvetica, sans-serif">

With one simple class, there is no
reason to generate API documentation. API documentation
makes sense when you have an application made up of a number
of complex classes that need documentation. The tool generates
<CODE>HTML</CODE> files (Web pages) that describe the class structures and contain
the text enclosed by doc comments.
The <A HREF="http://java.sun.com/products/jdk/javadoc/index.html">javadoc
Home Page</A> has more information on the <CODE>javadoc</CODE> command
and its output.

<A NAME="api"></A>
<H3>API Documentation</H3>

The Java platform installation includes API Documentation, which
describes the APIs available for you to use in your programs.
The files are stored in a <CODE>doc</CODE> directory beneath
the directory where you installed the platform. For example,
if the platform is installed in <CODE>/usr/local/java/jdk1.2</CODE>,
the API Documentation is in <CODE>/usr/local/java/jdk1.2/doc/api</CODE>.

<A NAME="more"></A>
<H3>More Information</H3>

See
<A HREF="http://java.sun.com/products/jdk/1.2/docs/tooldocs/tools.html">Java 2
SDK Tools</A> for more information on setting the class path and using
the <CODE>javac</CODE>, and <CODE>java</CODE> commands.

<P>
See
<A HREF="http://java.sun.com/docs/books/tutorial/getStarted/problems/index.html">Common 
Compiler and Interpreter Problems</A> lesson in
<A HREF="http://java.sun.com/docs/books/tutorial/trailmap.html">The Java
Tutorial</A> for troubleshooting help.

<P>
The <A HREF="http://java.sun.com/products/jdk/javadoc/index.html">javadoc
Home Page</A> has more information on the <CODE>javadoc</CODE> command
and its output.

<P>
You can also view the API Documentation for the Java 2 Platform on the 
<A HREF="http://java.sun.com/products/jdk/1.2/docs/api/index.html">java.sun.com</A> site. 

<P>
_______<BR>
<A NAME="TJVM"><SUP>1</SUP></A> As used on this web site, 
the terms &quot;Java virtual 
machine&quot; or &quot;JVM&quot; mean a virtual machine 
for the Java platform.

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