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How to update the value of a specific key in a HashMap in Kotlin

How to update the value of a specific key in a HashMap in Kotlin.

Here's a step-by-step tutorial on how to update the value of a specific key in a HashMap in Kotlin:

Step 1: Create a HashMap​

To begin, let's create a HashMap and populate it with some key-value pairs. Here's an example:

val hashMap = HashMap<String, Int>()
hashMap["key1"] = 10
hashMap["key2"] = 20
hashMap["key3"] = 30

In this example, we have a HashMap where the keys are of type String and the values are of type Int.

Step 2: Update the Value of a Key​

To update the value of a specific key, you can simply assign a new value to that key. Here's an example:

hashMap["key2"] = 25

In this example, we are updating the value of the key "key2" to 25. After this line of code, the value associated with "key2" in the HashMap will be changed to 25.

Step 3: Check the Updated Value​

To confirm that the value has been updated, you can retrieve the value of the key using the get() method. Here's an example:

val updatedValue = hashMap["key2"]
println(updatedValue)

In this example, we retrieve the value associated with "key2" and store it in the variable updatedValue. Then, we print the value to the console. In this case, the output will be 25.

Step 4: Handle Key Not Found​

If you try to update the value of a key that doesn't exist in the HashMap, a new key-value pair will be added instead. To avoid this, you can check if the key exists before updating the value. Here's an example:

if (hashMap.containsKey("key4")) {
    hashMap["key4"] = 40
} else {
    println("Key not found")
}

In this example, we check if the key "key4" exists in the HashMap using the containsKey() method. If it does, we update the value to 40. Otherwise, we print a message stating that the key was not found.

Step 5: Handle Null Values​

If you want to update the value of a key to null, you can assign null to that key. Here's an example:

hashMap["key2"] = null

In this example, we update the value of the key "key2" to null. After this line of code, the value associated with "key2" in the HashMap will be null.

That's it! You now know how to update the value of a specific key in a HashMap in Kotlin.