Javadoc build failure on JDK 15

When building javadoc of armeria ./gradlew javadoc:javadoc on JDK15 environment, I meet Javadoc build failure.

/Users/user/line/armeria/consul/src/main/java/com/linecorp/armeria/server/consul/ConsulUpdatingListenerBuilder.java:38: error: heading used out of sequence: <H3>, compared to implicit preceding heading: <H1>
 * <h3>Examples</h3>
   ^
/Users/user/line/armeria/consul/src/main/java/com/linecorp/armeria/client/consul/ConsulEndpointGroupBuilder.java:35: error: heading used out of sequence: <H3>, compared to implicit preceding heading: <H1>
 * <h3>Examples</h3>

AFAIK, the Armeria project is now based on JDK 14, so this issue is not a high-priority issue. But since JDK 14 is not an LTS version so in near future IMHO this issue is should be solved. And also please note that sdkman does not provide adopt JDK14 version already.

➜  ~ sdk list java
================================================================================
Available Java Versions
================================================================================
 Vendor        | Use | Version      | Dist    | Status     | Identifier
--------------------------------------------------------------------------------
 AdoptOpenJDK  |     | 15.0.2.j9    | adpt    |            | 15.0.2.j9-adpt
               |     | 15.0.2.hs    | adpt    | installed  | 15.0.2.hs-adpt
               |     | 11.0.10.j9   | adpt    |            | 11.0.10.j9-adpt
               |     | 11.0.10.hs   | adpt    |            | 11.0.10.hs-adpt
               |     | 11.0.9.hs    | adpt    | local only | 11.0.9.hs-adpt
               |     | 8.0.282.j9   | adpt    |            | 8.0.282.j9-adpt
               |     | 8.0.282.hs   | adpt    |            | 8.0.282.hs-adpt
 Amazon        |     | 15.0.2.7.1   | amzn    |            | 15.0.2.7.1-amzn
               |     | 15.0.1       | amzn    |            | 15.0.1-amzn
               |     | 15.0.1.9.1   | amzn    |            | 15.0.1.9.1-amzn
               |     | 11.0.10.9.1  | amzn    |            | 11.0.10.9.1-amzn
               |     | 8.282.08.1   | amzn    |            | 8.282.08.1-amzn
 Azul Zulu     |     | 15.0.2       | zulu    |            | 15.0.2-zulu
               |     | 15.0.2.fx    | zulu    |            | 15.0.2.fx-zulu
               |     | 15.0.1       | zulu    |            | 15.0.1-zulu
               |     | 15.0.1.fx    | zulu    |            | 15.0.1.fx-zulu
               | >>> | 14.0.2.fx    | zulu    | installed  | 14.0.2.fx-zulu
               |     | 13.0.5.fx    | zulu    |            | 13.0.5.fx-zulu
               |     | 11.0.10      | zulu    |            | 11.0.10-zulu
               |     | 11.0.10.fx   | zulu    |            | 11.0.10.fx-zulu
               |     | 11.0.9       | zulu    |            | 11.0.9-zulu
               |     | 11.0.9.fx    | zulu    |            | 11.0.9.fx-zulu
               |     | 8.0.282      | zulu    |            | 8.0.282-zulu
               |     | 8.0.282.fx   | zulu    |            | 8.0.282.fx-zulu
               |     | 8.0.275.fx   | zulu    |            | 8.0.275.fx-zulu
               |     | 7.0.282      | zulu    |            | 7.0.282-zulu
 BellSoft      |     | 15.0.2.fx    | librca  |            | 15.0.2.fx-librca
               |     | 15.0.2       | librca  |            | 15.0.2-librca
               |     | 11.0.10.fx   | librca  |            | 11.0.10.fx-librca
               |     | 11.0.10      | librca  |            | 11.0.10-librca
               |     | 8.0.282.fx   | librca  |            | 8.0.282.fx-librca
               |     | 8.0.282      | librca  |            | 8.0.282-librca
 GraalVM       |     | 21.0.0.r11   | grl     | local only | 21.0.0.r11-grl
               |     | 21.0.0.2.r11 | grl     |            | 21.0.0.2.r11-grl
               |     | 21.0.0.2.r8  | grl     |            | 21.0.0.2.r8-grl
               |     | 20.3.1.2.r11 | grl     |            | 20.3.1.2.r11-grl
               |     | 20.3.1.2.r8  | grl     |            | 20.3.1.2.r8-grl
               |     | 19.3.5.r11   | grl     |            | 19.3.5.r11-grl
               |     | 19.3.5.r8    | grl     |            | 19.3.5.r8-grl
 Java.net      |     | 17.ea.10     | open    |            | 17.ea.10-open
               |     | 17.ea.9      | open    |            | 17.ea.9-open
               |     | 17.ea.2.pma  | open    |            | 17.ea.2.pma-open
               |     | 17.ea.2.lm   | open    |            | 17.ea.2.lm-open
               |     | 17.ea.1.pma  | open    |            | 17.ea.1.pma-open
               |     | 16.ea.36     | open    |            | 16.ea.36-open
               |     | 15.0.2       | open    |            | 15.0.2-open
               |     | 11.0.2       | open    |            | 11.0.2-open
 SAP           |     | 15.0.2       | sapmchn |            | 15.0.2-sapmchn
               |     | 11.0.10      | sapmchn |            | 11.0.10-sapmchn
 TravaOpenJDK  |     | 11.0.9       | trava   |            | 11.0.9-trava
               |     | 8.0.232      | trava   |            | 8.0.232-trava
================================================================================
Use the Identifier for installation:

    $ sdk install java 11.0.3.hs-adpt
================================================================================

Related issue: https://bugs.openjdk.java.net/browse/JDK-8223552

[ikhoon]

There are two problems with JDK 15. One is h3 tags in Javadoc. Another one is Proguard. We could focus on Javadoc with this issue and probably create a separate issue on Proguard?

[minwoox]

https://github.com/Guardsquare/proguard/issues/64#issuecomment-755295941 Proguard will support JDK 15 soon.

I’m also fine using Shadow. BTW, what’s the benefit?