https://checkstyle.org/checks/javadoc/javadoctype.html#JavadocType
/var/tmp $ javac Test.java
# success
/var/tmp $ cat checkstyle.xml
<!DOCTYPE module PUBLIC
"-//Checkstyle//DTD Checkstyle Configuration 1.3//EN"
"https://checkstyle.org/dtds/configuration_1_3.dtd">
<module name="Checker">
<module name="TreeWalker">
<module name="JavadocType"/>
</module>
</module>
/var/tmp $ cat Test.java
/**
* <pre>{@code
* @Internal
* class Other {
* @Nullable String test(String param) {
* }
* }
* }</pre>
*/
public class Test {
public void test(String param) {
}
}
/var/tmp $ java -jar checkstyle-10.21.0-all.jar -c checkstyle.xml test.java
Starting audit...
[ERROR] /Users/jake/Projects/Java/checkstyle-test/Test.java:3:4: Unknown tag 'Internal'. [JavadocType]
[ERROR] /Users/jake/Projects/Java/checkstyle-test/Test.java:5:6: Unknown tag 'Nullable'. [JavadocType]
Audit done.
Checkstyle ends with 2 errors.
@Internal and @Nullable should not be reported as an unknown tag. It is inside a valid pre/code tag combo which is displayed correctly by the javadoc tool. You can see the rendered html below.

https://checkstyle.org/checks/javadoc/javadoctype.html#JavadocType
@Internaland@Nullableshould not be reported as an unknown tag. It is inside a valid pre/code tag combo which is displayed correctly by the javadoc tool. You can see the rendered html below.