将 List[String] 转换为 Map[String,String]

Question

Anyone help me to convert list of strings into Map by indexes: (0,1) as key-value pair and index(2,3) as 2nd pair and index(3,4) as 3rd pair.

Example: List("asd","fgh","qwe","tyu") into Map("asd"->"fgh", "qwe"->"tyu")

Answer 1

A simple matter of turning pairs into tuples and calling .toMap on it.

val myMap = myList.grouped(2)
                  .collect{
                    case List(a,b) => (a,b)
                    case List(x) => (x,"")
                  }.toMap

Note: This doesn't check for duplicate keys so an input like List("a","b","a","c") will result in Map("a" -> "c") .

Answer 2

This can be done using three standard library methods:

val list = List("asd","fgh","qwe","tyu")

list
  .grouped(2) // Group elements in pairs
  .map {      // Convert pairs to tuples
    case a :: b :: Nil => a -> b   // Normal values to tuple
    case a :: Nil      => a -> ""  // Final value if list size is odd
  }
  .toMap // Convert List[(A, B)] to Map[A,B]

Since you are creating a Map , if the same even value appears more than once there will be duplicate keys, and only the final pair will be in the resulting Map .

(If you are new to Scala, the syntax a -> b is another way of creating a tuple (a, b) , and can be used in cases like this to make it clear that there is a key-value relationship between values in a pair)