Hello.java API Document

Java Tools Tutorials - Herong's Tutorial Examples

∟Hello.java API Document

This section provides a tutorial example of how to generated a Java API document for the Hello.java class with 'javadoc' command.

To get started learning the "javadoc" command, let's try it on the Hello.java program.

herong> more Hello.java

class Hello {
   public static void main(String[] a) {
      System.out.println("Hello world!");
   }
}

herong> javadoc Hello.java

Loading source file Hello.java...
Constructing Javadoc information...
error: No public or protected classes found to document.
1 error

Looks like "javadoc" only documents "protected" and "protected" classes by default. To make it work for the Hello class, we just need to specify the "-private" option.

herong$ javadoc -private Hello.java

Loading source file Hello.java...
Constructing Javadoc information...
Building index for all the packages and classes...
Standard Doclet version 17.0.1+12-LTS-39
Building tree for all the packages and classes...
Generating .\Hello.html...
Hello.java:1: warning: no comment
class Hello {
^
Hello.java:2: warning: no comment
   public static void main(String[] a) {
                      ^
Generating .\package-summary.html...
Generating .\package-tree.html...
Generating .\overview-tree.html...
Building index for all classes...
Generating .\allclasses-index.html...
Generating .\allpackages-index.html...
Generating .\index-all.html...
Generating .\index.html...
Generating .\help-doc.html...
2 warnings

Not too bad. I only got 2 warnings: "no comment" on the "Hello" class and "no comment" on the "main()" method.

Now, let's what files are generated by "javadoc":

herong$ ls -l

-rw-r--r--   7784  Hello.html
-rw-r--r--    107  Hello.java
-rw-r--r--   3395  allclasses-index.html
-rw-r--r--   3366  allpackages-index.html
-rw-r--r--   3043  constant-values.html
-rw-r--r--   2958  deprecated-list.html
-rw-r--r--     16  element-list
-rw-r--r--   7878  help-doc.html
-rw-r--r--   3989  index-all.html
-rw-r--r--    869  index.html
-rw-r--r--    464  jquery-ui.overrides.css
-rw-r--r--    189  member-search-index.js
-rw-r--r--     45  module-search-index.js
-rw-r--r--   3092  overview-tree.html
-rw-r--r--     95  package-search-index.js
-rw-r--r--   3451  package-summary.html
-rw-r--r--   3209  package-tree.html
drwxr-xr-x    136  resources
drwxr-xr-x    238  script-dir
-rw-r--r--   2565  script.js
-rw-r--r--  13238  search.js
-rw-r--r--  19763  stylesheet.css
-rw-r--r--     42  tag-search-index.js
-rw-r--r--    120  type-search-index.js
20 File(s)         75,410 bytes

Wow! "javadoc" generated so many files for just a single short Java class file.

As you can see from the file list, Java API documents are generated as Web files (HTML documents). If you open "index.html" in a Web browser, you should see the "Hello" class API document nicely displayed.