Build: Fix javadoc errors with Oracle JDK

Tested with 12.0.2

core/java/src/org/json/simple/parser/Yylex.java

@@ -383,7 +383,7 @@ int getPosition(){
    *
    * All internal variables are reset, the old input stream 
    * <b>cannot</b> be reused (internal buffer is discarded and lost).
-   * Lexical state is set to <tt>ZZ_INITIAL</tt>.
+   * Lexical state is set to <code>ZZ_INITIAL</code>.
    *
    * @param reader   the new input stream 
    */
@@ -425,7 +425,7 @@ int getPosition(){
 
 
   /**
-   * Returns the character at position <tt>pos</tt> from the 
+   * Returns the character at position <code>pos</code> from the 
    * matched text. 
    * 
    * It is equivalent to yytext().charAt(pos), but faster