The **``kotlin.collections``** package is part of Kotlin's standard library, and 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 backing storage.

#    
## The `removeAll()` method
The `ArrayList` class contains the **`removeAll()`** method which removes all the elements present in the specified input collection from the array list.

## Syntax
```kotlin
fun removeAll(elements: Collection<E>): Boolean
```

## Arguments 
- This method takes a collection of elements as input.

## Return value
- It returns `true` if any of the elements from the specified collection are removed and `false` if the array list is not modified.



The illustration below shows the function of the `removeAll()` method:

fun main(args : Array<String>) {
    val monthList = ArrayList<String>()
    
    monthList.add("January")
    monthList.add("February")  
    monthList.add("March")  
    monthList.add("April")      
    monthList.add("May")      
    println("Printing ArrayList elements --")  
    println(monthList)  

    val oddMonths = ArrayList<String>()
    oddMonths.add("March")
    oddMonths.add("May")  
    
    monthList.removeAll(oddMonths)
    println("Printing ArrayList elements after calling removeAll() --")     
    println(monthList)    
}

## Explanation
- **Line 2**: We create an empty array list named `monthList` to store the strings.

- **Lines 4-8**: We add a few months' names to the `monthList` object using the `add()` method.
- **Lines 12-14**: We create another collection `oddMonths` containing the name of a few months to be deleted.
- **Line 16**: We call the `removeAll()` method and pass the collection `oddMonths`  created above as input. It removes all the elements of the input collection that are present in the array list.

- **Line 18**: We print the elements of `monthList` after removing `oddMonths`. 

The `ArrayList` elements before and after calling `removeAll()` method are displayed using the `println()` function of the `kotlin.io` package.

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

Removes elements in a specified collection from an ArrayList, returning true if modified.

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

The removeAll() method

Syntax

Arguments

Return value

Example

Explanation

The `removeAll()` method