Exception
Prerequisites:
try catch
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var str: String? = null
try {
println(str!!.length)
} catch (e: KotlinNullPointerException) {
e.printStackTrace()
}
Exception in thread "main" java.lang.NullPointerException
at LearnNullKt.testNull(LearnNull.kt:53)
at LearnNullKt.main(LearnNull.kt:62)
at LearnNullKt.main(LearnNull.kt)
自訂例外
Prerequisites:
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class MyNullException : RuntimeException("空值")
fun checkNull(str: String?) {
str ?: throw MyNullException()
}
fun main() {
var str: String? = null
try {
checkNull(str)
} catch (e: Exception) {
println(e)
}
}
MyNullException: 空值
precondition functions
以下是kotlin提供的檢查值為null或值為false，所拋出的異常。
| 函式 | 檢查項目 | Exception thrown |
|---|---|---|
| checkNotNull | null | IllegalStateException |
| require | false | IllegalArgumentException |
| requireNotNull | null | IllegalStateException |
| error | null | IllegalStateException |
| assert | false | AssertError |
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var str: String? = null
try {
checkNotNull(str) {"空值"}
} catch (e: Exception) {
println(e)
}
java.lang.IllegalStateException: 空值