How can I create an array in Kotlin like in Java by just providing a size?

Question

How can I create a Array like we do in java?

int A[] = new int[N];

How can I do this in Kotlin?

Answer 1

According to the reference, arrays are created in the following way:

• For Java's primitive types there are distinct types IntArray, DoubleArray etc. 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, false for Boolean.

• Non primitive-arrays are represented by Array<T> class, where T is the items type.

  T can still be one of types primitive in Java (Int, Boolean,...), but the values inside will be boxed equivalently to Java's Integer, Double and so on.

  Also, T can be both nullable and non-null like String and String?.

  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 }
  

Answer 2

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.