What is the ArrayList.isEmpty() method in Kotlin?

The kotlin.collections package is part of Kotlin’s standard library.

It contains all collection types, such as:

  • Map
  • List
  • Set, etc.

The package provides the ArrayList class, which is a mutable list and uses a dynamic resizable array as the backing storage.

The isEmpty() method

The ArrayList class contains the isEmpty() method, which is used to check if the array list is empty or not.

If the list does not have any elements, it returns true. Otherwise, it returns false.

Syntax

fun isEmpty(): Boolean

Arguments

  • This method does not take any arguments.

Return value

  • It returns true if the list is empty, and false otherwise.

Things to note

  • ArrayList follows the sequence of insertion of elements.

  • It is allowed to contain duplicate elements.

The illustration below shows the function of the isEmpty() method.

Checking if the array list is empty using the isEmpty() method

Code

The ArrayList class is present in the kotlin.collection package and is imported by default in every Kotlin program.

fun main(args : Array<String>) {
val companyList = ArrayList<String>()
companyList.add("Apple")
companyList.add("Google")
companyList.add("Microsoft")
val emptyList = ArrayList<String>()
println("Printing companyList elements--")
println(companyList)
println("Printing emptyList elements--")
println(emptyList)
println("Checking if companyList is empty using isEmpty() : ${companyList.isEmpty()}")
println("Checking if emptyList is empty using isEmpty() : ${emptyList.isEmpty()}")
}

Explanation

  • First, we create an empty array list named companyList to store the strings.

  • Next, we use the add() method to add a few company names to the ArrayList object, such as: "Google", "Apple", "Microsoft", and "Netflix".

  • We create another empty array list, emptyList.

  • Next, we call the isEmpty() method on the companyList and it returns false, as it has few elements.

  • We again call the isEmpty() method on the emptyList and it returns true.

  • The array list elements and result of isEmpty() method are displayed using the print() function of the kotlin.io package.

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