用好 Require,check,assert,写好 Kotlin 代码

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var isDiskMounted = true

fun createNewFile(file: File?): Boolean {
return if (isDiskMounted) {
if (file != null) {
file.createNewFile()
if (file.exists()) {
true
} else {
println(“Create file($file) failed”)
false
}
} else {
println(“File($file) is null”)
false
}
} else {
println(“Disk is not mounted”)
false
}
}

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fun createNewFileV2(file: File?): Boolean {
check(isDiskMounted) {
“Disk is not mounted”
}

requireNotNull(file) {
“file is null”
}

file.createNewFile()

assert(file.exists()) {
“createNewFileV2 file($file) does not exist”
}
return true
}

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fun readFileContent(file: File?): String {
//判断file不能为null
requireNotNull(file)

//判断文件必须可读，并提供错误的信息
require(file.canRead()) {
“readFileContent file($file) is not readable”
}

//read file content
return “Your file content”
}

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class Engine {
var isStarted = false

fun speedUp() {
check(isStarted) {
“Engine is not started, cannot be speed up now”
}

//speed up the engine
}

}

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fun makeFile(path: String) {
val file = File(path)
file.createNewFile()

assert(file.exists()) {
“make File($file) failed”
}
}

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fun main() {
createNewFile(null)
safeRun {
createNewFileV2(null)
}
}

private val isDebug = true

fun safeRun(block: () -> Unit) {
try {
block()
} catch (t: Throwable) {
t.printStackTrace()
if (isDebug) {
throw t
}
}
}