jsonParser1.kt

fun jsonParser1(){
    val json = """{"a":1, "b":"abc", "c":true, "d":null}"""


    val map:HashMap<String, Any?> = hashMapOf()
    map["a"] = 1
    map["b"] = "abc"
    map["c"] = true
    map["d"] = null

    //map을 하나의 문자열로 바꾼다
    var result:String = "{"

    var isFirst = true
    for(entry in map){
        if(isFirst) isFirst = false else result += ", "
        result += """"${entry.key}":"""
        if(entry.value is String) result += """"${entry.value}"""" else result += "${entry.value}"

    }

    result += "}"

    // file로 만들어서 저장한다
    val file = java.io.File("save.txt")
    file.writeText(result)
}

jsonParser2.kt

import java.io.File

fun jsonParser2(){
    val json = """{"a":1, "b":"abc", "c":true, "d":[1,2,3], "e":{"x":1, "y":"abc"}}"""


    val map:HashMap<String, Any?> = hashMapOf()
    map["a"] = 1
    map["b"] = "abc"
    map["c"] = true
    map["d"] = listOf(mapOf("x" to 1, "y" to "abc"), listOf(1,2,3),3)
    map["e"] = mapOf("x" to 1, "y" to "abc", "c" to listOf(1,2,3))

    var homework = hashMapOf<String, Any?>(
        "target" to map,
        "previous" to null
    )
    var result:String = ""
    var limit:Int = 10
    while(limit-- > 0){
        result += when(val v = homework["target"]){
            is String->""""$v""""
            is List<*>->{
                var str = if(homework["isFirst"] == null) "[" else ""
                var isFirst = if(homework["isFirst"] == null) true.also{homework["isFirst"] = false} else false
                val iter =
                    (homework["iter"] as? MutableIterator<Any?>) ?: v.iterator().also { homework["iter"] = it }
                var isBreak = false
                while(iter.hasNext()){
                    val v: Any? = iter.next()
                    if(isFirst) isFirst = false else str += ", "
                    str += when(v){
                        is String->""""$v""""
                        is Map<*,*>, is List<*>-> {
                            val newWork = hashMapOf<String, Any?>(
                                "target" to v,
                                "previous" to homework
                            )
                            homework = newWork
                            isBreak = true
                            break
                        }
                        else->"$v"
                    }
                }
                str + if(!isBreak){
                    homework = homework["previous"] as? HashMap<String, Any?> ?: break
                    "]"
                } else ""
            }
            is Map<*,*>->{
                var str = if(homework["isFirst"] == null) "{" else ""
                var isFirst = if(homework["isFirst"] == null) true.also{homework["isFirst"] = false} else false
                val iter =
                    (homework["iter"] as? MutableIterator<MutableMap.MutableEntry<String, Any?>>) ?: v.iterator().also { homework["iter"] = it }
                var isBreak = false
                while(iter.hasNext()){
                    val entry = iter.next()
                    if(isFirst) isFirst = false else str += ", "
                    str += """"${entry.key}":"""
                    str += when(val v = entry.value){
                        is String->""""$v""""
                        is Map<*,*>, is List<*>-> {
                            val newWork = hashMapOf<String, Any?>(
                                "target" to v,
                                "previous" to homework
                            )
                            homework = newWork
                            isBreak = true
                            break
                        }
                        else->"$v"
                    }
                }
                str + if(!isBreak) {
                    homework = homework["previous"] as? HashMap<String, Any?> ?: break
                    "}"
                }else ""
            }
            else->"$v"
        }
        println(result)
    }
    result += "}"
    // file로 만들어서 저장한다
    val file = File("save.txt")
    file.writeText(result)
}