How to use the isNullOrEmpty method of MutableList in Kotlin

Overview

The isNullOrEmpty method returns True if the MutableList is either null or empty.

Syntax

fun <T> Collection<T>?.isNullOrEmpty(): Boolean

Parameter

This method doesn’t take any argument.

Return value

This method returns a Boolean value. Returns True if the MutableList is null or empty. Otherwise, False is returned.

Code

The below code demonstrates how to use the isNullOrEmpty method:

fun main() {
  // create a null list
  val nullList: MutableList<Any>? = null
  println("nullList is =>$nullList")
  println("nullList.isNullOrEmpty() => ${nullList.isNullOrEmpty()}") // true
  // create an empty list
  val emptyList= mutableListOf<Int>()
  println("\nemptyList is =>$emptyList")
  println("emptyList.isNullOrEmpty() => ${emptyList.isNullOrEmpty()}") // true
  // create an non-empty and not-null list
  val validList = mutableListOf(1)
  println("\nvalidList is =>$validList")
  println("validList.isNullOrEmpty() => ${validList.isNullOrEmpty()}") // false
}

Explanation

  • Line 3: We create a variable nullList with type as MultableList and assign null as value.

  • Line 5: We call the isNullOrEmpty method of the nullList. The value of the nullList variable is null so True is returned.

  • Line 8: We create an empty MultableList (variable name nullList) by calling the multableListOf method without argument.

  • Line 10: We call the isNullOrEmpty method of the emptyList. The emptyList contains no elements so True is returned.

  • Line 13: We create a MultableList(variable name validList) by calling the multableListOf method with the 1 and 2 argument. The multableListOf method returns an MultableList object with [1,2] as elements.

  • Line 15: We call the isNullOrEmpty method of the validList. The validList contains two elements so False is returned.

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