Scala、Spark 中 == 和 === 的区别
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Difference between == and === in Scala, Spark
提问by Avijit
I am from a Java background and new to Scala.
我来自 Java 背景并且是 Scala 的新手。
I am using Scala and Spark. But I'm not able to understand where I use ==and ===.
我正在使用 Scala 和 Spark。但我无法理解我在哪里使用==和===。
Could anyone let me know in which scenario I need to use these two operators, and what's are difference between ==and ===?
任何人都可以让我知道在这种情况下，我需要使用这两个运营商，以及什么是区别==和===？
回答by Christian Fries
The "==" is using the equalsmethods which checks if the two references point to the same object. The definition of "===" depends on the context/object. For Spark , "===" is using the equalTomethod.
See
" ==" 正在使用equals检查两个引用是否指向同一个对象的方法。" ==="的定义取决于上下文/对象。对于 Spark ，“ ===” 正在使用该equalTo方法。看
- 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)
- 对于
==https://spark.apache.org/docs/2.0.0/api/java/org/apache/spark/sql/Column.html#equals(java.lang.Object) - 对于
===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:
（因为您引用的是 Spark ：）Spark 的一个重要区别是返回值。对于列：
==returns a boolean===returns a column (which contains the result of the comparisons of the elements of two columns)
==返回一个布尔值===返回一列（其中包含两列元素的比较结果）
回答by Lifu Huang
Generally speaking, they are just functions.
一般来说，它们只是函数。
For different types, "==" and "===" might be defined or "overloaded" for different meanings.
对于不同的类型，“==”和“===”可能被定义或“重载”以获得不同的含义。
For example, in some test framework, "===" is defined for some special function. See this.
例如，在某些测试框架中，为某些特殊功能定义了“===”。看到这个。
回答by Aditya Agarwal
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:
ScalaTest 允许您使用 Scala 的断言语法，但定义了一个三等号运算符 (===) 以提供更好的错误消息。下面的代码会给你一个错误，表明断言失败：
assert(1 == 2) Using triple equals instead would give you the more informative error message, "1 did not equal 2":
assert(1 === 2)
assert(1 == 2) 改用三重等于会给您提供更多信息的错误消息，“1 不等于 2”：
断言（1 === 2）
have a look at this page for more details; What is the === (triple-equals) operator in Scala Koans?
查看此页面了解更多详情； Scala Koans 中的 === (triple-equals) 运算符是什么？
