Duplicate method error

I wrote a simple Kotlin program following:

class Foo() {

  private var foo: Int = 0

  fun getFoo(): Int {
  return foo


val f: Foo = Foo()

This code was compiled without any error, but I got a runtime error:

Exception in thread "main" java.lang.ClassFormatError: Duplicate method name&signature in class file main/Foo

I guess this is because the compiler implicitly creates getFoo() and setFoo(). Is this a bug? Are there any way to avoid this error?

I know accessors declaration is not recommended, but I want to write getters and setters to keep consistency with Java.

Hi Ziphil!

The methods “getFoo” and “setFoo” for property are generated exactly for java interop. So you write only

class Foo() {
  var foo: Int = 0

in Kotlin and you use it as


from Java.

If you want your custom getters and setters (not just return value and set value) you use the following syntax:

var foo: Int = 0   get() = $foo   private set(value: Int) {   doSomethingSpecial()   $foo = value   }

There is a very old request to forbig declaring functions with the same JVM signature (KT-1).
I’ve created another one specifically for your case (KT-4287).