Javadoc is deleted by reformat action.
If javadoc formatting setting there are all check boxes unchecked, except the first one (Format javadoc) 

Input code:
public class NewClass<T> {

    /**
     * Hello this is comment <b>very</b> long comment comment comment comment comment
     *
     * @param <S> Parameter
     * @param in Input
     * @param aaa Variable length argument
     * @return Something
     * @throws IOException error in the code
     */
    public <S> S neco(S in, String... aaa) throws IOException {
        return in;
    }
}

output:
public class NewClass<T> {

        @throws IOException error in the code
     */
    public <S> S neco(S in, String... aaa) throws IOException {
        return in;
    }
}