Kotlin 中 Java 静态最终字段的等价物是什么？
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What is the equivalent of Java static final fields in Kotlin?
提问by pdeva
In Java, to declare a constant, you do something like:
在 Java 中，要声明一个常量，您可以执行以下操作：
class Hello {
public static final int MAX_LEN = 20;
}
What is the equivalent in Kotlin?
Kotlin 中的等价物是什么？
采纳答案by Ruslan
According Kotlin documentationthis is equivalent:
根据 Kotlin文档，这是等效的：
class Hello {
companion object {
const val MAX_LEN = 20
}
}
Usage:
用法：
fun main(srgs: Array<String>) {
println(Hello.MAX_LEN)
}
Also this is static final property (field with getter):
这也是静态最终属性（带有 getter 的字段）：
class Hello {
companion object {
@JvmStatic val MAX_LEN = 20
}
}
And finally this is static final field:
最后这是静态最终字段：
class Hello {
companion object {
@JvmField val MAX_LEN = 20
}
}
回答by Gary LO
if you have an implementation in Hello, use companion objectinside a class
如果您有一个实现Hello，请companion object在类中使用
class Hello {
companion object {
val MAX_LEN = 1 + 1
}
}
if Hellois a pure singleton object
ifHello是一个纯单例对象
object Hello {
val MAX_LEN = 1 + 1
}
if the properties are compile-time constants, add a constkeyword
如果属性是编译时常量，则添加一个const关键字
object Hello {
const val MAX_LEN = 20
}
if you want to use it in Java, add @JvmStaticannotation
如果你想在Java中使用它，添加@JvmStatic注释
object Hello {
@JvmStatic val MAX_LEN = 20
}
回答by Simon Ludwig
For me
为了我
object Hello {
const val MAX_LEN = 20
}
was to much boilerplate. I simple put the static final fields above my class like this
太多样板了。我简单地将静态最终字段放在我的班级之上
val MIN_LENGTH = 10
class MyService{
}
