code: public JsonParserBuilder integerHandler(@Nullable IntegerHandler integerHandler) {
          checkNoConflict(integerHandler, "integer", numberHandler, "number");
          this.integerHandler = integerHandler;
          return this;
      }
docs: Sets the parser's integer value handler, or removes it if {@code null} is passed.
  
  @param integerHandler a new integer value handler. {@code null} means there shouldn't be a integer
  value handler in the built parser.
  @return a reference to this builder
  @throws java.lang.IllegalStateException if {@link #numberHandler()} is already set