小编use*_*782的帖子

我有一个简单的火花功能来测试DF窗口:

    import org.apache.spark.sql.{DataFrame, SparkSession}

    object ScratchPad {

      def main(args: Array[String]): Unit = {
        val spark = SparkSession.builder().master("local[*]").getOrCreate()
        spark.sparkContext.setLogLevel("ERROR")
        get_data_frame(spark).show()
      }

      def get_data_frame(spark: SparkSession): DataFrame = {
        import spark.sqlContext.implicits._
        val hr = spark.sparkContext.parallelize(List(
          ("Steinbeck", "Sales", 100),
          ("Woolf", "IT", 99),
          ("Wodehouse", "Sales", 250),
          ("Hemingway", "IT", 349)
        )
        ).toDF("emp", "dept", "sal")

        import org.apache.spark.sql.expressions.Window
        import org.apache.spark.sql.functions._

        val windowspec = Window.partitionBy($"dept").orderBy($"sal".desc)


        hr.withColumn("rank", row_number().over(windowspec))

      }
    }

我写了一个像这样的测试:

    import com.holdenkarau.spark.testing.DataFrameSuiteBase
    import org.apache.spark.sql.Row
    import org.apache.spark.sql.types._
    import org.scalatest.FunSuite

    class TestDF extends FunSuite with DataFrameSuiteBase  {

      test ("DFs equal") { …

我在一本java书中发现了这个,并想了解为什么我会收到如下所述的错误:

public class Wildcard<V> {

    V value;

    public Wildcard(V value) {
        super();
        this.value = value;
    }

    public V getValue() {
        return value;
    }

    public void setValue(V value) {
        this.value = value;
    }

    public boolean sameObj(Wildcard<? extends V> v1, MyComparator<V> comparator) {
        return comparator.compare(this.value, v1.value);
    }

    public static void main(String[] args) {

        Wildcard<Integer> iTest = new Wildcard<Integer>(10);
        Wildcard<Number> nTest = new Wildcard<Number>(10);
        nTest.sameObject(iTest, new MyComparator<Number>() {
            public boolean compare(Number o1, Number o2) {
                return o1 == o2;
            }
        });
    }
} …