Kotlin 接收器名称冲突

Question

当运行以下代码片段时，编译器正尝试根据 kotlin.collections 中定义的接收器解析方法 isEmpty，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，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() was added in Java 11. The Android version of Optional（或者你的目标是什么）没有。

只需使用 !isPresent()，或使用 kotlin 语法糖 !isPresent。

Kotlin 接收器名称冲突

Kotlin Receiver Name Clash

java

build

kotlin