Kotlin 异常处理

• • 1. kotlin 捕获异常
  • 2. kotlin 先处理小异常，再处理大异常
  • 3. kotlin 使用 throw 抛出异常
  • 4. kotlin 自定义异常
  • 附 Github 源码：

• 不论在 try 块、catch 块中执行怎样的代码（除非退出虚拟机 System.exit(1) ），finally 块的代码总会被执行

// 定义顶级常量
const val fileName = "src/com/william/testkt/exception_demo.txt"


fun writeFile(src: String): Int {
    var fos: FileOutputStream? = null
    try {
        val file = File(fileName)
        fos = FileOutputStream(file)
        fos.write(src.toByteArray())
        return 1 // 会被 finally 块中的代码覆盖
    } catch (e: Exception) {
        e.printStackTrace()
        return 2 // 会被 finally 块中的代码覆盖
    } finally {
        fos?.close()
        return 3
    }
}


fun readFile(): String {
    var fis: FileInputStream? = null
    try {
        val file = File(fileName)
        val size = file.length().toInt()
        fis = FileInputStream(file)
        val sb = StringBuilder()
        val buffer = ByteArray(size)
        fis.read(buffer)
        sb.append(String(buffer))
        return sb.toString()
    } catch (e: Exception) {
        e.printStackTrace() // 打印堆栈信息
        return "${e.message}"
    } finally {
        println("finally")
        fis?.close()
    }
}

fun main() {
    val result = writeFile("this is a simple message")
    println(result) // 3

    val text = readFile()
    println(text)
}

fun compute(obj: String?) {
    try {
        Integer.parseInt(obj)
    } catch (e: RuntimeException) {
        println("RuntimeException: ${e.message}")
    } catch (e: Exception) {
        println("Exception: ${e.message}")
    }
}

fun throwExFun(param: String?) {
    if (param == null) {
        throw NullPointerException()
    }
}

class CustomException : Exception {
    // 无参构造
    constructor() {}

    // 带参构造
    constructor(msg: String) : super(msg) {}
}

fun throwCustomExFun(param: String?) {
    if (param == null) {
 		// 使用 throw 抛出自定义异常
        throw CustomException("param is null")
    }
}

TestException.kt