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How to access elements in an ArrayList in Kotlin

How to access elements in an ArrayList in Kotlin.

Here is a step-by-step tutorial on how to access elements in an ArrayList in Kotlin.

Step 1: Create an ArrayList​

To begin, you need to create an ArrayList in Kotlin. An ArrayList is a dynamic array that can store elements of any type. You can create an ArrayList using the ArrayList class or the arrayListOf function.

val numbers = ArrayList<Int>()
numbers.add(1)
numbers.add(2)
numbers.add(3)

In the above example, we create an ArrayList called numbers and add three integers to it.

Step 2: Accessing elements by index​

Each element in an ArrayList has an index associated with it. You can access elements by their index using the square bracket notation. The index starts from 0 for the first element and goes up to size - 1.

val firstNumber = numbers[0]
val secondNumber = numbers[1]
val thirdNumber = numbers[2]

println(firstNumber)  // Output: 1
println(secondNumber) // Output: 2
println(thirdNumber)  // Output: 3

In the above example, we access the elements at index 0, 1, and 2 and print them to the console.

Step 3: Checking the size of the ArrayList​

You can get the number of elements in an ArrayList using the size property. It returns the size of the ArrayList as an integer.

val size = numbers.size
println(size) // Output: 3

In the above example, we get the size of the numbers ArrayList and print it to the console.

Step 4: Accessing elements using a loop​

You can iterate over the elements of an ArrayList using a loop. There are several types of loops available in Kotlin, such as for loop, while loop, and forEach loop.

for (number in numbers) {
    println(number)
}

numbers.forEach { number ->
    println(number)
}

In the above examples, we iterate over the numbers ArrayList and print each element to the console using a for loop and a forEach loop.

Step 5: Accessing elements using ListIterator​

You can also use a ListIterator to access elements in an ArrayList. The ListIterator provides methods for iterating over the elements in both forward and backward directions.

val iterator = numbers.listIterator()

while (iterator.hasNext()) {
    val number = iterator.next()
    println(number)
}

while (iterator.hasPrevious()) {
    val number = iterator.previous()
    println(number)
}

In the above example, we create a ListIterator for the numbers ArrayList and use it to iterate over the elements in both forward and backward directions.

That's it! You now know how to access elements in an ArrayList in Kotlin. You can use the square bracket notation, loops, or a ListIterator to access elements based on your requirements.