Kotlin Arrays

Kotlin 数组

Arrays are used to store multiple values in a single variable, instead of creating separate variables for each value.

To create an array, use the arrayOf() function, and place the values in a comma-separated list inside it

val cars = arrayOf("Volvo", "BMW", "Ford", "Mazda")

访问数组元素

You can access an array element by referring to the index number, inside square brackets.

In this example, we access the value of the first element in cars

val cars = arrayOf("Volvo", "BMW", "Ford", "Mazda")
println(cars[0])
// Outputs Volvo 

更改数组元素

要更改特定元素的值，请参考索引号：

cars[0] = "Opel"

Array Length / Size

To find out how many elements an array have, use the size property

val cars = arrayOf("Volvo", "BMW", "Ford", "Mazda")
println(cars.size)
// Outputs 4 

Check if an Element Exists

You can use the in operator to check if an element exists in an array

val cars = arrayOf("Volvo", "BMW", "Ford", "Mazda")
if ("Volvo" in cars) {
  println("It exists!")
} else {
  println("It does not exist.")
}

循环遍历数组

Often when you work with arrays, you need to loop through all of the elements.

You can loop through the array elements with the for loop, which you will learn even more about in the next chapter.

下面的示例输出了 cars 数组中的所有元素

val cars = arrayOf("Volvo", "BMW", "Ford", "Mazda")
for (x in cars) {
  println(x)
}