Java -> Kotlin equivalents

If your starting Kotlin with prior java knowledge, here's a quick lookup table for some common equivalents:

 

Java	Kotlin
Accessibility modifiers: private protected //default package private public	private protected Internal // accessible in module //default public
String [] anArray;	var anArray:Array<String>
(castType)	smart casting after is as
public class Area { private int length; private int width;   //constructor public Area(int length, int width){ this.length = length; this.width =  width; System.out.printf("Surface: %d",length*width); }   //accessor public int getCircumference(){ return 2*(length+width); } }	class Area(var length: Int , var width: Int) {             //to add onstructor code init { println("Surface: ${length * width}") }         //accessor val circumference get() = 2*(length + width)   }
anEnum.values()	anEnum.entries
class Shape{} class Rectangle extends Shape{}	open class Shape {} class Rectangle : Shape {}
final String aConstant="a";	val aConstant="a"
instanceOf	is
Primitives: int, double...	Int,Double...
lambda (shorter forms exist in both languages) BiFunction<Integer, Integer, Integer> mutiply= (a, b) -> { System.out.println("java lambda"); return a * b; };	val multiply: (Int, Int)->Int = { a, b -> println("kotlin lambda") a * b }
new Random();	Random();
Object	Any?
public static void main(String[] args){} // Note: Java 22 has a preview of a main() function	fun main(args:Array<String>){}
static	companion top level function const
switch expression	when
int ternaryVar=test?1:2;	var ternaryVar = if(test) 1 else 2;
throw UnsupportedOperationException	TODO()
void	Unit