How can I create a Array like we do in java?
int A[] = new int[N];
How can I do this in Kotlin?
6 Answers
According to the reference, arrays are created in the following way:
For Java's primitive types there are distinct types
IntArray,DoubleArrayetc. which store unboxed values.They are created with the corresponding constructors and factory functions:
val arrayOfZeros = IntArray(size) //equivalent in Java: new int[size] val numbersFromOne = IntArray(size) { it + 1 } val myInts = intArrayOf(1, 1, 2, 3, 5, 8, 13, 21)The first one is simillar to that in Java, it just creates a primitive array filled with the default value, e.g. zero for
Int,falseforBoolean.Non primitive-arrays are represented by
Array<T>class, whereTis the items type.Tcan still be one of types primitive in Java (Int,Boolean,...), but the values inside will be boxed equivalently to Java'sInteger,Doubleand so on.Also,
Tcan be both nullable and non-null likeStringandString?.These are created in a similar way:
val nulls = arrayOfNulls<String>(size) //equivalent in Java: new String[size] val strings = Array(size) { "n = $it" } val myStrings = arrayOf("foo", "bar", "baz") val boxedInts = arrayOfNulls<Int>(size) //equivalent in Java: new Integer[size] val boxedZeros = Array(size) { 0 }
2 Comments
Kirill Rakhman
Array<Int>(size) doesn't compile. That's because you can't create a non-nullable array without providing the elements.
hotkey
@KirillRakhman, thanks for your remark, that was an inadvertent mistake. Fixed.
Here is simple example of init of Array of String
var names = Array<String>(<AnotherArray.size>) { i -> "" }
Kotlin doc
1 Comment
UnreachableCode
In practice, it looks like this
val array = Array<String?>(10){""} where 10 is me saying an array of 10 empty stringsIf you want to create an array of Primitive Types, you can simply use the constructors:
Example: to create an array of integers with size N.
val arr = IntArray(size = N)
For non-primitive types, you can use arrayOfNulls<Type>().
1 Comment
SMBiggs
Wow that works (arrayOfNulls), but it would have taken me years to figure that out. Thank god kotlin is so obvious and intuitive!
In Kotlin, creating an IntArray of size N is simple. Use IntArray(n) or the appropriate type, as detailed thoroughly in hotkey's answer.
When utilizing your fixed size array, you can use Kotlin Destructuring
// Create fixed sized array
val point = IntArray(2)
// Access values directly
val (x, y) = point
In this case, x will be taken from index 0, y from index 1, etc.
Comments
You can create it using IntArray like this declaration for variable
val A = IntArray(N)
Comments
val A = FloatArray(N) //N being the size of the ar
1 Comment
MathMax
The OP needs an array of integer, not floats.
int, but for Objects, there is stackoverflow.com/questions/32679060/…