Windowed
The windowed() function can fetch all possible ranges of collection of items on a given size. It returns a list of element ranges that you would see at the collection using sliding window of the particular size. It has optional two parameters:
step: distance between first item of every window. By default the value is 1, so the result contains windows starting from all elements. partialWindows: if true includes windows of smaller size left at the end.
Kotlin program to demonstrate windowed() function –
Java
fun main(args : Array<String>){ val fruits = listOf("apple", "banana", "cherries", "orange") println(fruits.windowed(3)) println(fruits.windowed( 3, step = 2, partialWindows = true))} |
Output:
[[apple, banana, cherries], [banana, cherries, orange]] [[apple, banana, cherries], [cherries, orange]]
There is a zipWithNext() function to build two element window, can also be called with a transformation.
Kotlin program to demonstrate zipWithNext()
Java
fun main(args : Array<String>){ val fruits = listOf("apple", "banana", "cherries", "dragon_fruit", "egg_fruit", "fig") println(fruits.zipWithNext())} |
Output:
[(apple, banana), (banana, cherries), (cherries, dragon_fruit), (dragon_fruit, egg_fruit), (egg_fruit, fig)]
Kotlin | Retrieve Collection Parts
The slice function allows you to extract a list of elements from a collection by specifying the indices of the elements you want to retrieve. The resulting list contains only the elements at the specified indices. The subList function allows you to retrieve a sublist of a collection by specifying the start and end indices of the sublist. The resulting sublist contains all the elements between the specified indices, inclusive of the start index but exclusive of the end index. We will explore both of these functions with code examples to demonstrate how to use them to retrieve collection parts in Kotlin. In Kotlin, you can retrieve parts of a collection using the slice function or the subList function. The slice function allows you to extract a list of elements from a collection by specifying the indices of the elements you want to retrieve.
Example:
Kotlin
fun main() { val list = listOf("a", "b", "c", "d", "e") val indices = listOf(1, 3) val result1 = list.slice(indices) println(result1) // Output: [b, d] val result2 = list.subList(1, 4) println(result2) // Output: [b, c, d]} |
Output:
[b, d] [b, c, d]
In this example, we first create a list called list containing five elements. We then create a new list called indices containing the indices of the elements we want to retrieve using the slice function.
We call the slice function on list and pass in indices as a parameter, and the resulting list is stored in the result1 variable. We then print out the contents of result1, which is [b, d].
We then use the subList function to retrieve a sublist of list containing elements from index 1 to index 4 (exclusive). The resulting sublist is stored in the result2 variable, and we print out the contents of result2, which is [b, c, d].
Kotlin provides extension functions for retrieving collection parts. A member function defined outside the class is called an extension function. These extension functions can provide a variety of ways to select different items from the list.
Four extension functions are:
- Slice
- Take and Drop
- Chunked
- Windowed