Skip to main content

How to iterate over a LinkedList in Kotlin

How to iterate over a LinkedList in Kotlin.

How to Iterate Over a LinkedList in Kotlin

In Kotlin, a LinkedList is a data structure that represents a collection of elements in a specific order. It allows for efficient insertion and removal of elements at both the beginning and end of the list. In this tutorial, we will explore different ways to iterate over a LinkedList in Kotlin.

Creating a LinkedList​

Before we dive into iterating over a LinkedList, let's first create one. In Kotlin, you can create a LinkedList using the LinkedList class from the java.util package. Here's an example:

import java.util.LinkedList

fun main() {
    val linkedList = LinkedList<String>()
    linkedList.add("apple")
    linkedList.add("banana")
    linkedList.add("orange")
    println(linkedList)
}

In the code above, we import the LinkedList class and create a new instance of it. We then add three elements to the list: "apple", "banana", and "orange". Finally, we print the contents of the linked list, which will output [apple, banana, orange].

Iterating Over a LinkedList using a For Loop​

One way to iterate over a LinkedList in Kotlin is by using a for loop. Here's an example:

import java.util.LinkedList

fun main() {
    val linkedList = LinkedList<String>()
    linkedList.add("apple")
    linkedList.add("banana")
    linkedList.add("orange")
    
    for (item in linkedList) {
        println(item)
    }
}

In the code above, we iterate over the linkedList using a for loop. The loop variable item represents each element in the list, and we simply print it out. This will output:

apple
banana
orange

Iterating Over a LinkedList using an Iterator​

Another way to iterate over a LinkedList in Kotlin is by using an iterator. The LinkedList class provides an iterator() function that returns an iterator object. Here's an example:

import java.util.LinkedList

fun main() {
    val linkedList = LinkedList<String>()
    linkedList.add("apple")
    linkedList.add("banana")
    linkedList.add("orange")
    
    val iterator = linkedList.iterator()
    
    while (iterator.hasNext()) {
        val item = iterator.next()
        println(item)
    }
}

In the code above, we obtain an iterator object using the iterator() function of the linkedList. We then use a while loop to iterate over the elements. The hasNext() function checks if there are more elements, and the next() function returns the current element and moves the iterator to the next one. This will output the same result as the previous example:

apple
banana
orange

Iterating Over a LinkedList using forEach​

Kotlin provides a convenient forEach function that allows us to iterate over a collection and perform an action on each element. Here's an example of using forEach with a LinkedList:

import java.util.LinkedList

fun main() {
    val linkedList = LinkedList<String>()
    linkedList.add("apple")
    linkedList.add("banana")
    linkedList.add("orange")
    
    linkedList.forEach { item ->
        println(item)
    }
}

In the code above, we call the forEach function on the linkedList and pass a lambda expression as the argument. The lambda expression takes each element (item) and performs an action on it, which in this case is printing it out. This will produce the same output as the previous examples:

apple
banana
orange

Conclusion​

In this tutorial, we learned different ways to iterate over a LinkedList in Kotlin. We explored using a for loop, an iterator, and the forEach function. Depending on your specific use case, you can choose the method that best suits your needs.