code: public @NotNull QueryBuilder appendPlaceholders(int count) {
          if (count <= 0) throw new IllegalArgumentException("count must be positive, but was: " + count);
  
          query.append('?');
          for (int i = 1; i < count; i++)
              query.append(",?");
  
          return this;
      }
  
      /**
       * Adds placeholders for all elements of collection and then adds then values
       * of collection itself.
       */
      public @NotNull QueryBuilder appendPlaceholders(@NotNull Collection<?> args) {
          appendPlaceholders(args.size());
          addArguments(args);
  
          return this;
      }
  
      /**
       * Is the query string empty?
       */
      public boolean isEmpty() {
         return query.length() == 0;
      }
  
      /**
       * Does this query have any arguments?
       */
      public boolean hasArguments() {
          return !arguments.isEmpty();
      }
  
      /**
       * Adds an argument to this query.
       */
      public @NotNull QueryBuilder addArgument(@Nullable Object argument) {
          arguments.add(argument);
          return this;
      }
  
      /**
       * Adds given arguments to this query.
       */
      public @NotNull QueryBuilder addArguments(Object... args) {
          return addArguments(asList(args));
      }
  
      /**
       * Adds given arguments to this query.
       */
      public @NotNull QueryBuilder addArguments(@NotNull Collection<?> args) {
          arguments.addAll(args);
          return this;
      }
  
      /**
       * Builds an SQL query from the current state of this builder.
       *
       * @throws IllegalStateException if the builder is empty
       */
      public @NotNull SqlQuery build() {
          if (query.length() == 0)
              throw new IllegalStateException("empty query");
  
          return SqlQuery.query(query.toString(), new ArrayList<>(arguments));
      }
  }
docs: Adds a given amount of comma-separated place-holders. The amount must be at last 1.