The following doc comment causes two breakiterator messages to appear.

/**
 * The class implements interfaces (i.e. specifically Interface1).
 * This second sentence does not appear in the summary.
 */

This produces the long message when this sentence is parsed for index-all.html,
and produces the short message when this sentence is again parsed for package-summary.html
Does it need to be parsed twice? Perhaps there is a good case to leave it as-is.

I've attached the full Class1.java test case.
Here is the error stream, starting with the version number:

Standard Doclet version 1.4.0

Generating html-messagetests/constant-values.html...
Building tree for all the packages and classes...
Building index for all the packages and classes...
Generating html-messagetests/overview-tree.html...
Generating html-messagetests/index-all.html...
./Class1.java:33: warning - The first sentence is interpreted to be:
"The class implements interfaces (i.e."
This sentence is different from what will be interpreted as the first sentence in the
next major release (when that interpretation will be internationalized), which is:
"The class implements interfaces (i.e. specifically Interface1 and
 Interface2). "
To avoid this note, change the doc comment to make this a proper first sentence, then
use -breakiterator from that point forward, which will output this new sentence.
./Class1.java:38: warning - <a> tag is malformed:
"Here is a malformed link: <a href"http://java.sun.com/">Java</a>"
./Class1.java:99: warning - Tag @link: can't find publicMethod() in com.package1.Class1
Generating html-messagetests/deprecated-list.html...
./Class1.java:99: warning - Tag @link: can't find publicMethod() in com.package1.Class1
Building index for all classes...
Generating html-messagetests/allclasses-frame.html...
Generating html-messagetests/allclasses-noframe.html...
Generating html-messagetests/index.html...
Generating html-messagetests/packages.html...
Generating html-messagetests/com/package1/package-frame.html...
Generating html-messagetests/com/package1/package-summary.html...
./Class1.java:33: warning - The first sentence is interpreted to be:
"The class implements interfaces (i.e."
This sentence is different from what would be generated using -breakiterator:
"The class implements interfaces (i.e. specifically Interface1 and
 Interface2). "