FULL PRODUCT VERSION :
java version "1.8.0_144"
Java(TM) SE Runtime Environment (build 1.8.0_144-b01)
Java HotSpot(TM) 64-Bit Server VM (build 25.144-b01, mixed mode)

ADDITIONAL OS VERSION INFORMATION :
Linux MiWiFi-R1CM-srv 3.10.0-514.26.2.el7.x86_64 #1 SMP Tue Jul 4 15:04:05 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux

A DESCRIPTION OF THE PROBLEM :
The first Doc#firstSentenceTags() returns different number of tags when we use html tag or javadoc tag in it.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
1) add javadoc with html tag to one field (e.z. "The {@code ++} (postfix increment) operator.");
2) add the same javadoc but replacing html tag by javadoc tag to the second filed (e.z. "The <code>++</code> (postfix increment) operator.");
3) Parse javadoc into RootDoc;
4) Compare the results of Doc#firstSentenceTags()

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
number of tags is equal when javadoc is used, it is represented as three tags instead of one when html tag is used
ACTUAL -
number of tags is different when javadoc is used, it is represented as three tags instead of one when html tag is used.

ERROR MESSAGES/STACK TRACES THAT OCCUR :
no error occurs

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
//should be located accessible to test class
/**
 * The {@code ++} (postfix increment) operator.
 */
public class JavadocParseError {
    /**
     * The <code>++</code> (postfix increment) operator.
     */
    public static final String CONST = "abc";
}

public class JavadocParseTest {

    @Test
    public void testJavadocParsedIncorrectly() throws Exception {
        final ListBuffer<String[]> options = new ListBuffer<>();
        options.add(new String[] {"-destfile", "target/tokentypes.properties"});

        final ListBuffer<String> names = new ListBuffer<>();
        names.add("JavadocParseError.java");

        final Context context = new Context();
        new TestMessager(context);
        final JavadocTool javadocTool = JavadocTool.make0(context);
        final RootDoc rootDoc = getRootDoc(javadocTool, options, names);
        final ClassDoc[] classes = rootDoc.classes();
        assertEquals("Should parse first sentence: " + classes[0].fields()[0].commentText()
                        + "- into one tag. Actual tags: "
                        + Arrays.toString(classes[0].fields()[0].firstSentenceTags()),
                1, classes[0].fields()[0].firstSentenceTags().length);
        assertEquals("Should parse first sentence: " + classes[0].commentText()
                        + "- into one tag. Actual tags: "
                        + Arrays.toString(classes[0].firstSentenceTags()),
                1, classes[0].firstSentenceTags().length);
    }

    private static RootDoc getRootDoc(JavadocTool javadocTool, ListBuffer<String[]> options,
                                      ListBuffer<String> names) throws Exception {
        final Method getRootDocImpl = getMethodGetRootDocImplByReflection();
        return (RootDoc) getRootDocImpl.invoke(javadocTool, "", "UTF-8",
                    new ModifierFilter(ModifierFilter.ALL_ACCESS),
                    names.toList(),
                    options.toList(),
                    new ListBuffer<JavaFileObject>().toList(),
                    false,
                    new ListBuffer<String>().toList(),
                    new ListBuffer<String>().toList(),
                    false, false, false);
    }

    private static Method getMethodGetRootDocImplByReflection() throws ClassNotFoundException {
        Method result = null;
        final Class<?> javadocToolClass = Class.forName("com.sun.tools.javadoc.JavadocTool");
        final Method[] methods = javadocToolClass.getMethods();
        for (Method method: methods) {
            if ("getRootDocImpl".equals(method.getName())) {
                result = method;
            }
        }
        return result;
    }

    private static class TestMessager extends Messager {

        private final List<String> messages = new ArrayList<>();

        TestMessager(Context context) {
            super(context, "");
        }

        @Override
        public void printError(String message) {
            messages.add(message);
        }
    }
}
---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
We need to check that number of tags is not greater than 1, for that purpose we can skip all "Text" tags from validation or just stay with html tags.