Java - Spark SQL DataFrame map function is not working

Question

In Spark SQL when I tried to use map function on DataFrame then I am getting below error.

The method map(Function1, ClassTag) in the type DataFrame is not applicab

Answer 1

No need to convert to RDD, its delays the execution it can be done as below

`public static void mapMethod() { // Read the data from file, where the file is in the classpath. Dataset df = sparkSession.read().json("file1.json");

// Prior to java 1.8 
Encoder encoder = Encoders.STRING();
    List rowsList = df.map((new MapFunction() {
        private static final long serialVersionUID = 1L;

        @Override
        public String call(Row row) throws Exception {
            return "string:>" + row.getString(0).toString() + "<";
        }
    }), encoder).collectAsList();

// from java 1.8 onwards
List rowsList1 = df.map((row -> "string >" + row.getString(0) + "<" ), encoder).collectAsList();
System.out.println(">>> " + rowsList);
System.out.println(">>> " + rowsList1);

}`