override fun toString()

constructor(type: String)

A: fun foo(parentId: Long, itemId: Long) 
B: fun foo(itemId: Long, parentId: Long)

QueryRunner().query()

Long

val query = "SELECT COUNT(*) FROM goods_user_rel WHERE _goods_id = ?"
val count = QueryRunner().query(connection, query, ScalarHandler<Long>(), goodsId)

ScalarHandler<Int>()

java.lang.ClassCastException: java.lang.Long cannot be cast to java.lang.Integer

ScalarHandler<Int>()

ScalarHandler<Long>()

Long

class Myclass(val name: String, val age: Int) {
    private someProperty = .....
    private someProperty = .....
    companion object {
        @JvmStatic
        val instance = Myclass(name = ??  , age = ??)
    }
}

abstract class ParentObject(val id: Int)
class ChildObject(id: Int, val value: String) : ParentObject(id)

sealed class ParentObject(val id: Int)
data class ChildObject(id: Int, val value: String) : ParentObject(id)

interface Foo { val text: String }

class Bar (private var text2: String) : Foo {
    init {
        text2 = text2.replace('a', 'z')
    }
    override val text: String
        get() = text2
}

data class Foo(val a: String) {
    
    init {
        //magic that takes string and sets it to a
    }
}

var Bar : Foo = "b"

@Controller
class FileServerController {
    @RequestMapping(value = ["/**"])
    fun getFile(request: HttpServletRequest, response: HttpServletResponse): FileSystemResource {
        var fileName = request.servletPath
        val HOME = System.getenv("HOME")

        println("Requested ${fileName}")

        fileName = "${HOME}${fileName}"
        val file = File(fileName)

        if (file.canRead()) {
            println("Serving ${fileName}")
            if(fileName.endsWith(".xml")) {
                response.contentType = "text/xml"
            } else if(fileName.endsWith(".xslt")) {
                response.contentType = "application/xslt+xml"
            }
            return FileSystemResource(file)
        } else {
            println("Couldn't find ${fileName}")
            throw NotFoundException(fileName)
        }
    }
}

<dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>
    <dependency>
        <groupId>org.jetbrains.kotlin</groupId>
        <artifactId>kotlin-reflect</artifactId>
    </dependency>
    <dependency>
        <groupId>org.jetbrains.kotlin</groupId>
        <artifactId>kotlin-stdlib-jdk8</artifactId>
    </dependency>

Class<T>

override fun toType(): Class<Boolean?> = 
        Boolean::class.java as Class<Boolean?>

Unchecked cast Class<Boolean> to Class<Boolean?>

Int?

Integer

fun <T : User>gen(): List<T> = listOf(User())

userLocation

it.userlocation.forEach

val listOfLists = listOf(
     Data(1, listOf("A")),
     Data(2, listOf("B")),
     Data(1, listOf("B")),
     Data(2, listOf("C"))
  )
   output:  [ Data(1,listOf("A","B")) , Data(2,listOf("B","C"))]

target?.let { targetList.sortedWith(compareBy {it.priority == 1})}

interface SaveListener {
    fun onSave(name: String)
 }

myController.listener = object : SaveListener {
    override fun onSave(name: String) {
        //do thing
    }
}

myController.listener = SaveListener { //do thing }

val pickableState = try {
            PickableState.valueOf(state)
        } catch (ex: Exception){
            null
        }

PickableState.values().singleOrNull { it.name == state }