在 Kotlin 中一次定义多个变量(例如 Java : String x,y,z;) [英] Define multiple variables at once in Kotlin (e.g Java : String x,y,z;)

问题描述

我想知道是否有任何方法可以像 Java 和世界上几乎所有其他现有语言一样在 Kotlin 中同时定义多个变量.

I was wondering if there is any way to define multiple variables in Kotlin at once like in Java and almost every other existing language in the world .

就像在 Java 中一样:

like in Java :

String x = "Hello World!", y = null, z;

推荐答案

您可以声明(和分配)多个 变量在一行中使用分号 (;):

You can declare (and assign) multiple variables in one line by using semicolons (;):

val number = 42; val message = "Hello world!";

您还可以声明(和分配)多个属性 同样在同一行:

You can also declare (and assign) multiple properties in the same line similarly:

class Example {
    var number = 42; var message = "Hello world!";
}

一个可运行的例子示出了两个见解，您可以在 tio.run 在线尝试(它在我使用 Kotlin 1.1.2-5 版(JRE 1.8)的本地环境中也运行良好.0_144-b01)):

A runnable example illustrating both insights that you can try online at tio.run (it also worked fine in my local environment using Kotlin version 1.1.2-5 (JRE 1.8.0_144-b01)):

class Example {
    // declaring multiple properties in a single line
    var number:Int; var message:String;

    // constructor that modifies the parameters to emphasize the differences
    constructor(_number:Int, _message:String) {
        number = _number * 2
        message = _message.toUpperCase()
    }
}

fun main(args: Array<String>) {
    // declaring multiple read-only variables in a single line
    val number = 42; val message = "Hello world!";
    
    // printing those local variables
    println("[main].number = " + number)
    println("[main].message = " + message)
    
    // instantiating an object and printing its properties' values
    val obj = Example(number,message)
    println("[Example].number = " + obj.number)
    println("[Example].message = " + obj.message)
}

执行输出:

[main].number = 42
[main].message = Hello world!
[Example].number = 84
[Example].message = HELLO WORLD!

作为一个矛盾的旁注，在这个问题和答案，JetBrains 的工程师 yole 指出:

As a contradictory side note, in this question and answer, JetBrains' Engineer yole states that:

"在同一行上声明多个属性是不赞成的许多 Java 风格指南，所以我们没有实现对它的支持科特林."

"Declaring multiple properties on the same line is frowned upon by many Java style guides, so we did not implement support for that in Kotlin."

请注意，他的回答已经超过 4 年了，所以从那时起可能会有变化.

Note that his answer is more than 4-years old, so there could have been changes since then.

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