What I did when I converted java to Kotlin

Overview

I'm scribbling down how to solve the error I got when converting from Java to Kotlin with the Inttellij feature. I may organize it later. I'm a Kotlin beginner and I just erased the error for the time being, so there seems to be a place where it is badly written programmatically. Please let me know if there is a better solution.

Case study

If you have generics, you absolutely have to put it on

For the time being, I attached all <*>

before

var controller: Controller

after

var controller: Controller<*>

If you set the generics to <*>, an error will occur in the method that takes the generics as an argument.

<\ > Seems to be an abbreviation for \ , and out seems to be a restriction that uses generics only as a return value. There was a big difference in generics from Java around here, and I couldn't solve it by stopping thinking. For the time being, I had no choice but to look at the program and put in something other than <>. I'm not sure about kotlin's generics.

before

var controller: Controller

after

var controller: Controller<Data>

I can't have circular generics

This time it was just wasteful, so I erased one side and solved it. There was a method to make a new type and solve it by force, but linguistically, maybe it's about making circular generics.

Getter setter

It disappeared by conversion. In Kotlin, write to access the field as it is. Visibility seems to be read-only by declaring a private set.

before

game.getFinishStatus()

after

game.finishStatus

before

game.setFinishStatus(FinishStatus(true))

after

game.finishStatus=FinishStatus(true)

override

Overridden methods must have the override modifier. It's usually attached automatically, but there were some who didn't. Can you automatically add method overrides for Objects such as toString? Some of them weren't attached even in their own class. I'm not sure.

before

    fun toString(): String {
        return text
    }

after

    override fun toString(): String {
        return text
    }

list add

Kotlin's default list does not allow you to add or remove elements. If you declare it as List in Java, it will be converted to the default list, so add cannot be used. Rewrite the declaration to MutableList.

before

private var commandList: List<IN>? = null
commandList!!.add(command)//error

after

private var commandList: MutableList<IN>? = null
commandList!!.add(command)//No error

list remove

The one whose argument is the index is removeAt

before

shapeList.remove(0)

after

shapeList.removeAt(0)

cast

It disappeared for some reason. If you are doing a safe cast, it seems that there is no problem even if you delete the cast, but there was an error. Maybe it was a cast using Generics.

before

cd//originally(IN)cd //IN is generics

after

cd as IN

Variadic argument assignment

Since the type is different between the variable length argument and the normally declared array, it cannot be assigned. Create a new array from variable length arguments and assign.

before

class ControllerGroup(vararg controllers: Controller<*>) {
    private val controllers: Array<Controller<*>>
    init {
        this.controllers = controllers
    }
}

after

class ControllerGroup(vararg controllers: Controller<*>) {
    private val controllers: Array<Controller<*>>
    init {
        this.controllers = arrayOf(*controllers)
    }
}

Null check for method arguments

Null check related is usually done automatically, but it seems that method arguments are not done?

before

        game.addShape(shape)//Shape?That's why it's said no

after

        game.addShape(shape!!)

Array to initialize later

When you want to remove from the Null check an array that is first filled with Null and then filled with values (resulting in no Null). If you are using Arrays.fill or something. Insert when initializing Array

before

val results = arrayOfNulls<RPSResult>(3)
Arrays.fill(results,RPSResult.DRAW)

after

val results = Array<RPSResult>(3,{RPSResult.DRAW})

static import It seems that you can't call a static method without giving a class name with static import.

before

import game.rps.shape.Shape.*
///////////////////////////////
val results = judgeAll(SCISSOR, SCISSOR, SCISSOR, SCISSOR)

after

val results = Shape.judgeAll(SCISSOR, SCISSOR, SCISSOR, SCISSOR)

The one that doesn't need null but will be initialized later

Add lateinit modifier

before

private var currentShape: Array<Shape?>

after

private lateinit var currentShape: Array<Shape?>

Put an array directly in a variadic argument

• At the beginning

before

 Shape.judgeAll(currentShapes)

after

 Shape.judgeAll(*currentShapes)

toArray toTypedArray

before

currentList.toArray(arrayOfNulls<Shape>(currentList.size))

after

currentList.toTypedArray()

reference

I've given all the ones I've seen for the time being, so some of them have nothing to do with the information I wrote here, and I've definitely forgotten some. https://qiita.com/k5n/items/c8bf7a507b64f20eebd0 https://qiita.com/tasogarei/items/266ecf02576d48fc69f6 https://stackoverflow.com/questions/46682455/how-to-solve-violation-of-finite-bound-restriction-in-kotlin https://qiita.com/ssuzaki/items/8a550fca6775c1e6e147 https://qiita.com/k5n/items/18adb5c3503a54e96c22 https://qiita.com/ke__kyukyun1828/items/3832d0bf42e6f7ef150a https://qiita.com/koher/items/d9411a00986f14683a3f https://dogwood008.github.io/kotlin-web-site-ja/docs/reference/packages.html https://qiita.com/k5n/items/cc0377b75d8537ef8a85