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Print an uninitialized local variable
The statement in the following code fragment attempts to fetch and print a value using the uninitialized local variable named ref .
void doIt(){
char[]ref;
System.out.print(ref); As a result, the program refuses to compile, displaying the following error message under JDK 1.3.
Ap158.java:23: variable ref might not have been initialized
System.out.print(ref); See explanation below.
The javadoc.exe program
When you download the JDK from Oracle, you receive a program named javadoc.exe in addition to several other programs.
The purpose of the javadoc program is to help you document the Java programs that you write. You create the documentation by running the javadoc program and specifying your source file or files as a command-line parameter. Forexample, you can generate documentation for this program by entering the following at the command line.
javadoc Ap157.java Produces HTML files as output
This will produce a large number of related HTML files containing documentation for the class named Ap157 . The primary HTML file is named Ap157.html . A file named index.html is also created. This file can be opened in a browser to provide a viewer for all of theinformation contained in the many related HTML files.
(As a labor saving device, you can also specify a group of input files to the javadoc program, using wildcard characters as appropriate, to cause theprogram to produce documentation files for each of the input files in a single run.)
Special documentation comments and directives
If you include comments in your source code that begin with
/**
and end with
*/
they will be picked up by the javadoc program and become part of the documentation.
In addition to comments, you can also enter a variety of special directives to the javadoc program as shown in the following program.
public class Ap157{/**
* Returns the character at the* specified index. An index ranges from
*<code>0</code>to
*<code>length() - 1</code>.
** @param index index of desired
* character.* @return the desired character.
*/public char charAt(int index) {
//Note, this method is not intended// to be operational. Rather, it
// is intended solely to illustrate// the generation of javadoc
// documentation for the parameter// and the return value.
return 'a';//return dummy char}//end charAt method
}//end class The @param and @return directives
The @param and @return directives in the source code shown above are used by the javadoc program for documenting information about parameters passed to and information returned from the method named charAt . The method definition follows the special javadoc comment.
C. OK
Public classes in separate files
This program meets the requirement identified in Question 5 . In particular, this program defines two public classes. The source code for each public classis stored in a separate file. Thus, the program compiles and executes successfully, producing the text OK on the screen.
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