import org.apache.spark.sql.api.java.UDF1; //导入依赖的package包/类
private void start() {
	SparkSession spark = SparkSession.builder().appName("CSV to Dataset").master("local").getOrCreate();

	//registers a new internal UDF
	spark.udf().register("x2Multiplier", new UDF1<Integer, Integer>() {
		private static final long serialVersionUID = -5372447039252716846L;

		@Override
		public Integer call(Integer x) {
			return x * 2;
		}
	}, DataTypes.IntegerType);

	String filename = "data/tuple-data-file.csv";
	Dataset<Row> df = spark.read().format("csv").option("inferSchema", "true")
			.option("header", "false").load(filename);
	df = df.withColumn("label", df.col("_c0")).drop("_c0");
	df = df.withColumn("value", df.col("_c1")).drop("_c1");
	df = df.withColumn("x2", callUDF("x2Multiplier", df.col("value").cast(DataTypes.IntegerType)));
	df.show();
}