How to change the following keys from the map without any variables full functional
HashMap(false -> List(20, 15, 20, 17), true -> List(50, 25, 45, 21, 100, 2000, 2100))
to
HashMap("String1" -> List(20, 15, 20, 17), "String2" -> List(50, 25, 45, 21, 100, 2000, 2100))
I tried with map and was able to change the keys to the same strings but not to different ones.
You can apply a map to all the items but focus only on the keys:
yourMap.map({ case (a, b) => (f(a), b) })
You can define f
to be a function or simply a constant map eg:
Map(false -> "String1", true -> "String2")
Putting it all together:
object HelloWorld {
def main(args: Array[String]) {
val m = Map(false -> List(20, 15, 20, 17), true -> List(50, 25, 45, 21, 100, 2000, 2100))
val f = Map(false -> "String1", true -> "String2")
val x = m.map({ case (a, b) => (f(a), b) })
System.out.println(x)
}
}
Yields the expected result:
Map(String1 -> List(20, 15, 20, 17), String2 -> List(50, 25, 45, 21, 100, 2000, 2100))
If you like one-liners you can also avoid a separate map / function:
yourMap.map({
x => x match {
case (false, v) => ("String1", v)
case (true, v) => ("String2", v)
}
})
Use a pattern matching anonymous function directly :
hashM
.map {
case (true, ints) => "String1" -> ints
case (false, ints) => "String2" -> ints
}
if you work with non-exhaustive pattern matching ie you also want to filter out safely some tuples from the collection then use collect
:
hashM
.collect {
case (true, ints) => "String1" -> ints
}
you'll get here:
Map(String1 -> List(50, 25, 45, 21, 100, 2000, 2100))
It's probably the most readable solution i can think of.
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