如何在java中将字符串id转换为整数

JavaRDD<Rating> ratings = feedbackRDD.map((Function<Document, Rating>) d -> new Rating(d.getInteger("user"), d.getInteger("product"), ((Number) d.get("rating")).doubleValue()));
 MatrixFactorizationModel model = ALS.train(JavaRDD.toRDD(ratings), 5, 10, 0.01);

要使用spark.mllib.recommendation库spark.mllib.recommendation.rating，要求两个值都是整数。在java中如何将字符串ID转换为整数？