我需要回傳所有串列項，在 forEach 中它作業正常，在回圈之外它只回傳最后一項。
fun scanAndConvertFile(): String {
val scanner = Scanner(System.`in`)
print("Enter path to file to convert: ")
val fileName: String = scanner.nextLine()
val bufferedReader: BufferedReader = File(fileName).bufferedReader()
var result = bufferedReader.use { it.readText() }
val header = result.substring(0, result.indexOf(":61:"))
val body = result.substring(result.indexOf(":61:"), result.lastIndexOf(":61:220131C6"))
val footer = result.substring(result.lastIndexOf(":61:220131C6"), result.length)
var list = body.split(":61:")
list = list.filter { it.isNotEmpty() }
list = list.map {
":61:$it"
}
list.forEach() {
val part1 = it.substring(0, it.indexOf("?20"))
var part2ToBePasted = it.substring(it.indexOf("?20"), it.indexOf("?00"))
part2ToBePasted = part2ToBePasted.drop(3)
val part3 = it.substring(it.indexOf("?00"), it.indexOf("?27"))
var part4ToPast = it.substring(it.indexOf("?27"), it.indexOf("?28"))
part4ToPast = part4ToPast.drop(3)
val part5 = it.substring(it.indexOf("?28"), it.length)
list = if(part4ToPast.equals("")) {
listOf(part1.plus("?20").plus(part2ToBePasted).plus(part3).plus("?27").plus(part4ToPast).plus(part5))
} else {
listOf(part1.plus("?20").plus(part4ToPast).plus(part3).plus("?27").plus(part4ToPast).plus(part5))
}
// println(list) - 效果很好
}
val converted = header.plus(list).plus(footer)
// println(converted) - 只列印串列的最后一個元素
return converted
}
uj5u.com熱心網友回復：
我試著清理一下你的代碼（當然不能保證，因為我沒有任何測驗資料）：
fun scanAndConvertFile(): String {
print("Enter path to file to convert: ")
val fileName: String = Scanner(System.`in`).nextLine()
val bufferedReader: BufferedReader = File(fileName).bufferedReader()
val result = bufferedReader.use { it.readText() }
val header = result.substring(0, result.indexOf(":61:"))
val footer = result.substring(result.lastIndexOf(":61:220131C6"), result.length)
val list = result
.substring(result.indexOf(":61:"), result.lastIndexOf(":61:220131C6"))
.split(":61:")
.filter { it.isNotEmpty() }
.map { ":61:$it" }
.map {
val indexOf00 = it.indexOf("?00")
val indexOf20 = it.indexOf("?20")
val indexOf27 = it.indexOf("?27")
val indexOf28 = it.indexOf("?28")
val substring27to28 = it.substring(indexOf27, indexOf28).drop(3)
it.substring(0, indexOf20)
.plus("?20")
.plus(if (substring27to28 == "") it.substring(indexOf20, indexOf00).drop(3) else substring27to28)
.plus(it.substring(indexOf00, indexOf27))
.plus("?27")
.plus(substring27to28)
.plus(it.substring(indexOf28, it.length))
}
return header.plus(list).plus(footer)
}
基本上你需要使用map而不是forEach來回傳一個串列。map用于轉換串列的每個元素，而使用forEach可以對每個元素執行操作，但不回傳串列。
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