How to remove elements from a HashMap in Kotlin

How to remove elements from a HashMap in Kotlin.

Here's a detailed step-by-step tutorial on how to remove elements from a HashMap in Kotlin:

1. Create a HashMap:

   • To begin, let's create a HashMap in Kotlin. A HashMap is a collection that stores key-value pairs, where each key is unique.
   • You can create a HashMap using the HashMap constructor or the hashMapOf function. Here's an example using the constructor:

   val hashMap = HashMap<Int, String>()
   • This creates an empty HashMap where the keys are of type Int and the values are of type String.

2. Add elements to the HashMap:

   • Before we can remove elements, let's add some elements to the HashMap. You can add elements using the put function.
   • The put function takes two parameters: the key and the value. Here's an example:

   hashMap.put(1, "Apple")
   hashMap.put(2, "Banana")
   hashMap.put(3, "Orange")
   • This adds three elements to the HashMap with keys 1, 2, and 3, and corresponding values "Apple", "Banana", and "Orange".

3. Remove elements by key:

   • To remove an element from the HashMap, you need to specify the key of the element you want to remove. You can use the remove function to do this.
   • The remove function takes the key as a parameter and removes the corresponding key-value pair from the HashMap. Here's an example:

   hashMap.remove(2)
   • This removes the element with key 2 from the HashMap, which has the value "Banana".

4. Remove elements by value:

   • If you want to remove an element based on its value rather than the key, you can use the removeIf function.
   • The removeIf function takes a lambda expression as a parameter, which specifies the condition for removing elements. Here's an example:

   hashMap.removeIf { it.value == "Orange" }
   • This removes the element with the value "Orange" from the HashMap.

5. Remove elements using iterator:

   • Another way to remove elements from a HashMap is by using an iterator. You can iterate over the HashMap using the iterator function and remove elements using the remove function of the iterator.
   • Here's an example:

   val iterator = hashMap.iterator()
   while (iterator.hasNext()) {
       val entry = iterator.next()
       if (entry.value == "Apple") {
           iterator.remove()
       }
   }
   • This removes all elements with the value "Apple" from the HashMap.

6. Clear the HashMap:

   • If you want to remove all elements from the HashMap, you can use the clear function. This clears all key-value pairs from the HashMap, making it empty.
   • Here's an example:

   hashMap.clear()
   • This clears all elements from the HashMap.

That's it! You now know how to remove elements from a HashMap in Kotlin. You can use the remove function to remove elements by key, the removeIf function to remove elements by value, or use an iterator to remove elements one by one. Additionally, you can use the clear function to remove all elements from the HashMap at once.