Difference between == and === in Scala, Spark

Question

I am from a Java background and new to Scala.

I am using Scala and Spark. But I'm not able to understand where I use ==and ===.

Could anyone let me know in which scenario I need to use these two operators, and what's are difference between == and ===?

Answer 1

The "==" is using the equals methods which checks if the two references point to the same object. The definition of "===" depends on the context/object. For Spark , "===" is using the equalTo method. See

• for == https://spark.apache.org/docs/2.0.0/api/java/org/apache/spark/sql/Column.html#equals(java.lang.Object)
• for === https://spark.apache.org/docs/2.0.0/api/java/org/apache/spark/sql/Column.html#equalTo(java.lang.Object)

(Since you are referencing Spark:) An important difference for Spark is the return value. For Column:

• == returns a boolean

• === returns a column (which contains the result of the comparisons of the elements of two columns)

Answer 2

Generally speaking, they are just functions.

For different types, "==" and "===" might be defined or "overloaded" for different meanings.

For example, in some test framework, "===" is defined for some special function. See this.

Answer 3

ScalaTest lets you use Scala's assertion syntax, but defines a triple equals operator (===) to give you better error messages. The following code would give you an error indicating only that an assertion failed:

assert(1 == 2) Using triple equals instead would give you the more informative error message, "1 did not equal 2":

assert(1 === 2)

have a look at this page for more details; What is the === (triple-equals) operator in Scala Koans?