Kotlin中Array(2){0}语句里的‘0’有什么作用？

Great question! Let's break down exactly what that {0} does in your array declaration.

First, let's look at the full constructor signature for Kotlin's Array class that you're using:

public inline constructor(size: Int, init: (Int) -> T)

This constructor takes two parameters:

1. The first is the size of the array (in your case, 2).
2. The second is an initialization lambda function (init) that's called once for each index in the array. It takes the index as an argument and returns the initial value for that position.

What does {0} mean here? #

The {0} is a simplified Kotlin lambda expression. Since the init function expects a parameter (the index), but you're not using it, Kotlin lets you omit the parameter name. This lambda essentially says: "No matter what index I'm given, return the value 0".

So when you write Array(2){0}, you're telling Kotlin:

• Create an array with 2 elements.
• Set the initial value of every element to 0.

Why changing it still works? #

In your code, you immediately overwrite the initial values with a[0] = 100 and a[1] = 200. That's why replacing 0 with another integer (like 5 or 1000) doesn't break the code—those initial values just get overwritten before you print anything. If you removed the assignment lines, you'd see the initial values instead:

fun main(args: Array<String>) { 
    var a = Array<Int>(2){5} 
    print(a[1]) // This would print 5 instead of 200
}

Bonus: Using the index in the initialization lambda #

You can also use the index parameter to set different initial values for each position. For example:

// Creates an array with values [0, 1]
var a = Array(2){ it } 
// Creates an array with values [10, 11]
var b = Array(2){ it + 10 }

Here, it is the default name for the single parameter in a lambda in Kotlin.

内容的提问来源于stack exchange，提问作者Sachin Varma