Kotlin 接收器名称冲突

Question

运行以下代码片段时，编译器尝试解析方法isEmpty针对kotlin.collections中定义的接收器，原因我不完全理解。 方法isEmpty在java.util.Optional中定义。 如果我将isEmpty替换为!isPresent ，则代码将按预期工作。

private fun getThreadCount(param: Optional<String>): Int {
        return if(param.isEmpty) {
            DEFAULT_THREAD_COUNT
        } else {
            val threads = param.get()
            try {
                threads.toInt()
            } catch (ex: NumberFormatException) {
                throw RuntimeException("Failed to parse threads parameter: $threads")
            }
        }
    }

> Task :compileKotlin FAILED
e: /home/.../TaskParams.kt: (51, 25): Function invocation 'isEmpty(...)' expected
e: /home/.../TaskParams.kt: (51, 25): Unresolved reference. None of the following 
candidates is applicable because of receiver type mismatch: 
public inline fun <T> Array<out ???>.isEmpty(): Boolean defined in kotlin.collections
public inline fun BooleanArray.isEmpty(): Boolean defined in kotlin.collections
public inline fun ByteArray.isEmpty(): Boolean defined in kotlin.collections
public inline fun CharArray.isEmpty(): Boolean defined in kotlin.collections
public inline fun CharSequence.isEmpty(): Boolean defined in kotlin.text
public inline fun DoubleArray.isEmpty(): Boolean defined in kotlin.collections
public inline fun FloatArray.isEmpty(): Boolean defined in kotlin.collections
public inline fun IntArray.isEmpty(): Boolean defined in kotlin.collections
public inline fun LongArray.isEmpty(): Boolean defined in kotlin.collections
public inline fun ShortArray.isEmpty(): Boolean defined in kotlin.collections

这是针对 Kotlin 1.3.72 编译的

Answer 1

java.util.Optional isEmpty()被添加到 Java 11. Android 版本的Optional （或任何你的目标没有）。

只需 go 与!isPresent()或!isPresent与 kotlin 语法糖。