It would be great if the “Convert Java to Kotlin” feature in IntelliJ would default to using the opt...

# intellij

[Chris Ruddell]

It would be great if the “Convert Java to Kotlin” feature in IntelliJ would default to using the optional ? notation instead of force-unwrapping (!!) everything. I understand the force-unwrapping allows it to be more in a state where it can compile, but I assume most of us go through and replace all those with optionals anyway to ensure null safety. If there is a way of changing that default behavior, please let me know.

[Alexey Belkov [JB]]

I believe J2K should be as smart as possible generally, so type inference and conversion should choose the most appropriate types (nullable/not null) and corresponding operators without a special setting.

Can you share a specific code example where J2K doesn't convert the code optimally? Please file an issue at http://kotl.in/issue.

[Chris Ruddell]

Here’s a simple example I wrote to illustrate:

public class Animal {
    private Dog dog;

    void adoptDog() {
        dog = new Dog();
    }

    void groomDog() {
        dog.hairColor = "";
        dog.bark();
    }

    static class Dog extends Animal {
        private String hairColor;
        
        void bark() {
            
        }
    }

}

[Chris Ruddell]

When you convert this to Kotlin, it results in:

class Animal {
    private var dog: Dog? = null
    fun adoptDog() {
        dog = Dog()
    }

    fun groomDog() {
        dog!!.hairColor = ""
        dog!!.bark()
    }

    internal class Dog : Animal() {
        private val hairColor: String? = null
        fun bark() {}
    }
}

In addition to the dog variable being forced unwrapped, it won’t even compile because it has marked hairColor as a val. I understand it’s not perfect and expect to go over the code after conversion, but force-unwrapping seems like a bad default option compared to simply calling dog?.hairColor = ""

[Alexey Belkov [JB]]

Thank you, I created a couple of issues: https://youtrack.jetbrains.com/issue/KTIJ-6067, https://youtrack.jetbrains.com/issue/KTIJ-6068. Please vote/watch.

[Chris Ruddell]

Thanks!