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This article introduces the relevant knowledge of "what are the symbols in scala". In the operation of actual cases, many people will encounter such a dilemma. Then let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

Symbols in Scala:

: three colon operators: indicates the concatenation operation of list

Val one = List (1 and 2) val two = List (4 and 5) val three = one:::two

The output is three: List [Int] = List (1, 2, 3, 4, 5, 6)

:: two colon operators: indicates the join operation between a normal element and a list

The _ N underscore numeric operator: used to access the Nth element of the tuple, the value of N starts at 1. The element access method of a tuple is different from an array because the element type of a tuple can be different.

-> returns a binary tuple

Return: (List [Int], List [Int]) = (List (1,2,3), List (4,5,6))

Change what is on the left to something on the right; it can be seen as a syntax candy for creating an instance of a function. There are three common operators:

= >: Example:Int = > String indicates that the input of the function is int type and string type is returned, which is the same as Function (Int,String)

() = >: Example: () = > T indicates that the function has no input parameters, but returns T

Unit= >: Unit is equivalent to no value, equivalent to Void in C++

_ has many meanings

1. Wildcard characters

Import org.apache.spark.SparkContext._

2. Anonymous function

3. Refer to each element in the collection. For example, filter elements in a list that are greater than a certain value

Val lst = List (1, 2, 3, 4, 5) val lstFilter = lst.filter (_ > 3)

4. Pattern matching can be used to get the team members of a tuple.

Val m = Map (1-> 2 for 2-> 4)

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