Compiling the package

Question

hi,it is the basic question.compiler gives error when i compile any class in any package.how can we compile the classes packed in any package not in defualt package.

Answer 1

Assume that your programs are part of a package named divelog, which is specified by the first line in each source file: package divelog;
Also assume that this directory (C:\javaT\myWork\) is part of the CLASSPATH list of directories.
Also assume that all the source files reside in this directory structure: C:\javaT\myWork\divelog\
Then a statement to compile a source file Named Divelog.java is:
C:\JavaT\myWork\>javac divelog\Divelog.java
Explanation:
Java starts looking for classes in the directory(s) listed in the classpath. In this case, one of the directories should be: C:\JavaT\myWork\ since it contains your divelog package.
Compiling
A class can either be part of a package (ie, no package statement at the top of the class.), or not.
If the class is not part of a package: Its source file needs to be in one of the classpath directories. To compile you use the command: javac SomeFile.java, from within the classpath directory that contains the file.
The class is part of a package (this case): The source file must be in a subdirectory structure that starts in one of the classpath directories. The subdirectory structure must match the package statement.
So, you generate a directory structure C:\javaT\myWork\divelog\ which is the [classpath directory + the package subdirectory structure], and place Divelog.java in it.
Then from the classpath directory (C:\JavaT\myWork\) use the command: javac divelog\Divelog.java
This creates a file, Divelog.class in the divelog directory. (The following is where people tend to get lost.) The correct name now, as far as java is concerned, is the combination of package name and class name: divelog.Divelog (note I omit the .class)
Running
To run a class that's not part of a package: From within the classpath directory that contains the class. use the command: java SomeFile
To run a class that is part of a package: From within the classpath directory (C:\JavaT\myWork\) use the command java divelog.Divelog (Note that this is analogous to the command for a class not in a package, you just use the fully qualified name)
Setting the Classpath:
http://java.sun.com/j2se/1.4.1/docs/tooldocs/windows/classpath.html
[NOTE: always start your classpath with ".;" which means the current directory.]
How Classes are Found:
http://java.sun.com/j2se/1.4.1/docs/tooldocs/findingclasses.html