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How to create and add elements to a HashMap in Kotlin

How to create and add elements to a HashMap in Kotlin.

Here's a step-by-step tutorial on how to create and add elements to a HashMap in Kotlin:

Step 1: Create a HashMap​

To create a HashMap, you need to use the HashMap class in Kotlin. You can create an empty HashMap or initialize it with some initial elements. Here's how you can create an empty HashMap:

val hashMap = HashMap<KeyType, ValueType>()

Replace KeyType with the type of your keys and ValueType with the type of your values.

Step 2: Add elements to the HashMap​

To add elements to a HashMap, you can use the put() method. The put() method takes two arguments: the key and the value. Here's an example of how to add elements to a HashMap:

hashMap.put(key1, value1)
hashMap.put(key2, value2)
hashMap.put(key3, value3)

Replace key1, key2, and key3 with the actual keys you want to use, and value1, value2, and value3 with the actual values you want to associate with those keys.

Alternatively, you can use the [] operator to add elements to a HashMap. Here's an example:

hashMap[key1] = value1
hashMap[key2] = value2
hashMap[key3] = value3

Step 3: Add elements using the putAll() method​

If you have a collection of key-value pairs that you want to add to a HashMap, you can use the putAll() method. The putAll() method takes another map as an argument and adds all its key-value pairs to the current HashMap. Here's an example:

val anotherMap = mapOf(key1 to value1, key2 to value2, key3 to value3)
hashMap.putAll(anotherMap)

Replace key1, key2, and key3 with the actual keys you want to use, and value1, value2, and value3 with the actual values you want to associate with those keys.

Step 4: Check if an element exists in the HashMap​

To check if a specific key exists in a HashMap, you can use the containsKey() method. This method returns true if the key exists in the HashMap, and false otherwise. Here's an example:

if (hashMap.containsKey(key)) {
    // Key exists in the HashMap
} else {
    // Key does not exist in the HashMap
}

Replace key with the actual key you want to check.

Step 5: Retrieve the value associated with a key​

To retrieve the value associated with a specific key in a HashMap, you can use the get() method. This method takes the key as an argument and returns the corresponding value. Here's an example:

val value = hashMap.get(key)

Replace key with the actual key you want to retrieve the value for.

That's it! You now know how to create a HashMap and add elements to it in Kotlin.