Skip to main content

How to join two ArrayLists in Kotlin

How to join two ArrayLists in Kotlin.

Here's a step-by-step tutorial on how to join two ArrayLists in Kotlin:

Step 1: Create two ArrayLists​

First, you need to create two ArrayLists that you want to join. Here's an example:

val list1 = arrayListOf("apple", "banana", "cherry")
val list2 = arrayListOf("orange", "grape", "watermelon")

Step 2: Use the plus operator​

Kotlin provides the plus operator (+) to concatenate two ArrayLists. You can use it to join the two ArrayLists created in the previous step. Here's an example:

val joinedList = list1 + list2

In this example, the plus operator (+) concatenates list1 and list2 and assigns the result to joinedList.

Step 3: Print the joined ArrayList​

You can print the joined ArrayList to verify the result. Here's an example:

println(joinedList)

This will output:

[apple, banana, cherry, orange, grape, watermelon]

Step 4: Join ArrayLists with duplicates​

If you want to join the ArrayLists while allowing duplicates, you can use the plus operator twice. Here's an example:

val joinedListWithDuplicates = list1 + list2 + list1

In this example, list1 and list2 are joined, and then list1 is appended again to the result.

Step 5: Print the joined ArrayList with duplicates​

You can print the joined ArrayList with duplicates to verify the result. Here's an example:

println(joinedListWithDuplicates)

This will output:

[apple, banana, cherry, orange, grape, watermelon, apple, banana, cherry]

Step 6: Create an empty ArrayList and add elements from both lists​

If you want to join the ArrayLists without using the plus operator, you can create an empty ArrayList and add elements from both lists. Here's an example:

val joinedListEmpty = ArrayList<String>()
joinedListEmpty.addAll(list1)
joinedListEmpty.addAll(list2)

In this example, an empty ArrayList joinedListEmpty is created, and elements from list1 and list2 are added using the addAll() method.

Step 7: Print the joined ArrayList created without plus operator​

You can print the joined ArrayList created without using the plus operator to verify the result. Here's an example:

println(joinedListEmpty)

This will output:

[apple, banana, cherry, orange, grape, watermelon]

That's it! You have successfully joined two ArrayLists in Kotlin. You can choose the method that suits your requirements and use it in your code.