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How to reverse a Map in Kotlin?
Kotlin provides four types of constructors to define and manipulate a HashMap. In this article, we will see how we can reverse a map using Kotlin library function.
A Map is a collection where data is stored as a key-value pair and the corresponding key has to be unique.
A HashMap is a collection class based on MutableMap interface and it does that by implementing the MutableMap interface of HashTable.
Example − Reverse using Iterable associate()
In this example, we will create a HashMmap and we will reverse the same using associate(). In this method, we will be creating a new map and we will map the value to the key and the key with the value.
fun main(args: Array<String>) {
var subject : HashMap<String, Int>
= HashMap<String, Int> ();
subject.put("Java" , 1);
subject.put("Kotlin" , 2);
subject.put("Python" , 3);
subject.put("SQL" , 4);
println(subject) // map before reversing
// interchanging key and value pair
val reversed = subject.entries.associate{(k,v)-> v to k}
println(reversed)
}Output
On execution, it will generate the following output −
{Java=1, Kotlin=2, Python=3, SQL=4}
{1=Java, 2=Kotlin, 3=Python, 4=SQL}
Updated on: 01-Mar-2022
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