SCT-7635 Create a wrapper for the is_null function. (#70)

Create a wrapper for the is_null function.

src/main/java/com/snowflake/snowpark_java/Column.java

@@ -236,6 +236,16 @@ public Column is_null() {
     return new Column(this.scalaColumn.is_null());
   }
 
+  /**
+   * Wrapper for is_null function.
+   *
+   * @return The result column object
+   * @since 1.10.0
+   */
+  public Column isNull() {
+    return is_null();
+  }
+
   /**
    * Is not null.
    *

src/main/scala/com/snowflake/snowpark/Column.scala

@@ -390,6 +390,14 @@ case class Column private[snowpark] (private[snowpark] val expr: Expression) ext
    */
   def is_null: Column = withExpr(IsNull(expr))
 
+  /**
+   * Wrapper for is_null function.
+   *
+   * @group op
+   * @since 1.10.0
+   */
+  def isNull: Column = is_null
+
   /**
    * Is not null.
    * @group op

src/test/java/com/snowflake/snowpark_test/JavaColumnSuite.java

@@ -117,6 +117,7 @@ public void isNull() {
     DataFrame data = getSession().sql("select * from values(1),(null) as T(a)");
     Row[] expected = {Row.create(false, true), Row.create(true, false)};
     checkAnswer(data.select(data.col("a").is_null(), data.col("a").is_not_null()), expected, false);
+    checkAnswer(data.select(data.col("a").isNull(), data.col("a").is_not_null()), expected, false);
   }
 
   @Test

src/test/scala/com/snowflake/snowpark_test/ColumnSuite.scala

@@ -123,6 +123,7 @@ class ColumnSuite extends TestData {
 
     assert(df.where(df("A").equal_nan).collect() sameElements Array[Row](Row(Double.NaN, 3)))
     assert(df.where(df("A").is_null).collect() sameElements Array[Row](Row(null, 2)))
+    assert(df.where(df("A").isNull).collect() sameElements Array[Row](Row(null, 2)))
     assert(
       df.where(df("A").is_not_null).collect() sameElements Array[Row](
         Row(1.1, 1),