Kotlin为什么不执行自动类型转换? [英] Why doesn't Kotlin perform automatic type-casting?

问题描述

var a : Double
a = Math.sin(10) // error: the integer literal does not conform to the expected type Double
a = Math.sin(10.0) //This compiles successfully
println(a)

为什么Kotlin不执行隐式类型转换并强迫我们传递确切的数据类型?

Why doesn't kotlin perform implicit type conversion and force us to pass the exact type of data?

fun sin(value: Double): Double // at kotlin documentation

推荐答案

我们都知道Kotlin同时具有不可为空的Int和可为空的Int?.

We all know that Kotlin has both non-nullable Int and nullable Int?.

当我们使用Int?时，会发生这种情况:Kotlin实际上在Kotlin需要可空引用时将JVM原语装箱"，因为它旨在消除代码中空引用的危险.

When we use Int? this happens: Kotlin actually 'boxes' JVM primitives when Kotlin needs a nullable reference since it's aimed at eliminating the danger of null references from code.

现在看一下:(假设这是一个可编译的代码)

Now look at this: (assuming this is a compilable code)

val a: Int? = 1
val b: Long? = a

Kotlin不会执行隐式类型转换，因为这种情况会发生.如果Kotlin进行了隐式类型转换，则b应该为1.但由于a是装箱的Int而b是装箱的Long，因此 a == b会产生false 并陷入矛盾，因为其==运算符会检查equals()和Long的equals()也会检查其他部分是否也是Long.

Kotlin doesn't perform implicit type conversion because of this thing happens. If Kotlin did implicit type conversions, b should be 1. but since a is a boxed Int and b is a boxed Long, a == b yields false and falls into contradiction, since its == operator checks for equals() and Long's equals() checks other part to be Long as well.

查看文档

• 科特林的明确转换
• https://kotlinlang.org/docs/reference/basic-types.html
• https://kotlinlang.org/docs/reference/equality.html

• Explicit Conversions in Kotlin
• https://kotlinlang.org/docs/reference/basic-types.html
• https://kotlinlang.org/docs/reference/equality.html

这篇关于Kotlin为什么不执行自动类型转换?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！