In Kotlin, how do I create an instance of a class where the class name is a variable? - kotlin

Question

I am writing a Graph class in Kotlin. Here's my code so far:
import java.util.*
class Graph<Class>(connectionProb: Double) {
// a general network class
val nodes = mutableListOf<Class>()
val connectionProb = connectionProb
val connections = hashMapOf<Class, MutableList<Class>>()
var nextID = 0
private fun createNode() {
// Here is where I need help
}
}
I want to be able to specify the node type for each Graph. The code above will compile, but I'm unsure how to initialize new nodes. The only argument I want to pass into each node, regardless of its type, is nextID.
Thanks!

Answer 1

First thing you should do is define a class for your graph node, and instead of maintaining a map for connections, let every node maintain a list of its connections.
So your code would look like this
class Graph<T>(connectionProb: Double) {
var nextId = 0
val nodes = mutableListOf<Node<T>>()
// Define a node class, so if you have graph of Integer then you want a node of Integer
class Node<T>(var id: Int){
val connections = mutableListOf<Node<T>>()
fun addConnection(newConnection: Node<T>){
connections.add(newConnection)
}
override fun toString() = "$id"
/** add other functions, such as remove etc */
}
fun createNode(){
var newNode = Node<T>(nextId++)
nodes.add(newNode)
}
}
Now to use this graph you will do followig
fun main(){
var myGraph = Graph<Integer>(10.9)
myGraph.createNode()
myGraph.createNode()
myGraph.nodes[0].addConnection(myGraph.nodes[1])
/* Print all nodes in graph */
for(node in myGraph.nodes) print(" $node")
/* Print connections of first node */
for(node in myGraph.nodes[0].connections) print("\n\nConnection id: $node")
}
Please note that this will give you a general idea of how to go about implementing graph and there are many things that you can improve in the implementation. To learn more I suggest you read a good book, such as Data Structures and Algorithms in Java