How to Merge Maps In Kotlin?

To merge maps in Kotlin, you can use the plus operator (+) to combine two maps together. This will create a new map that contains all the key-value pairs from both maps. If there are any duplicate keys, the value from the second map will override the value from the first map.

Here is an example of how to merge two maps in Kotlin:

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fun main() {
    val map1 = mapOf("a" to 1, "b" to 2)
    val map2 = mapOf("b" to 3, "c" to 4)

    val mergedMap = map1 + map2

    println(mergedMap) // Output: {a=1, b=3, c=4}
}

In this example, map1 contains key-value pairs "a" to 1 and "b" to 2, and map2 contains key-value pairs "b" to 3 and "c" to 4. By using the + operator, we merge the two maps together into mergedMap, which now contains key-value pairs from both maps. The value for key "b" is overridden by the value from map2.

This way, you can easily merge multiple maps together in Kotlin.

How to merge maps in Kotlin with custom merge strategies for conflicting keys?

To merge maps in Kotlin with custom merge strategies for conflicting keys, you can use the merge function along with a lambda function to specify the custom merge strategy.

Here's an example code snippet demonstrating how to merge two maps with a custom merge strategy for conflicting keys:

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fun main() {
    val map1 = mapOf("key1" to 1, "key2" to 2)
    val map2 = mapOf("key2" to 20, "key3" to 30)

    val mergedMap = map1.toMutableMap()
    map2.forEach { (key, value) ->
        mergedMap.merge(key, value) { existingValue, newValue ->
            // Custom merge strategy: sum the values for conflicting keys
            existingValue + newValue
        }
    }

    println(mergedMap)
}

In this example, we first create two maps map1 and map2. Then, we create a mutable copy of map1 called mergedMap. We iterate over each key-value pair in map2 and use the merge function to merge the values into mergedMap. We provide a lambda function as the third parameter to merge, which specifies the custom merge strategy (summing the values for conflicting keys).

After merging the maps, we print out the resulting merged map.

You can modify the custom merge strategy lambda function to implement different merge strategies based on your specific requirements.

How to merge maps in Kotlin without modifying the original maps?

To merge two maps in Kotlin without modifying the original maps, you can create a new map that contains all key-value pairs from both maps. Here is an example of how you can do this:

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fun main() {
    val map1 = mapOf("A" to 1, "B" to 2)
    val map2 = mapOf("C" to 3, "D" to 4)

    val mergedMap = map1 + map2

    println("Map 1: $map1")
    println("Map 2: $map2")
    println("Merged map: $mergedMap")
}

In the above example, we use the + operator to merge map1 and map2 into a new map called mergedMap. The original maps map1 and map2 remain unchanged.

Alternatively, you can also use the plus function to merge the maps like this:

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val mergedMap = map1.plus(map2)

Both approaches will create a new map that contains all key-value pairs from both maps without modifying the original maps.

How to merge maps in Kotlin with nullable values?

To merge maps in Kotlin with nullable values, you can use the plus operator along with the merge function. Here's a simple example:

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fun main() {
    val map1: Map<String, Int?> = mapOf("a" to 1, "b" to null)
    val map2: Map<String, Int?> = mapOf("b" to 2, "c" to null)

    // Merge two maps using the plus operator
    val mergedMap = map1 + map2

    println("Merged Map: $mergedMap")

    // Merge two maps using the merge function
    val mergedMap2 = map1.toMutableMap()
    map2.forEach { (key, value) -> mergedMap2.merge(key, value) { oldValue, newValue -> oldValue ?: newValue } }

    println("Merged Map 2: $mergedMap2")
}

In this example, map1 and map2 are maps with nullable values. We use the + operator to merge the two maps, which will overwrite any duplicate keys from the second map with the values from the second map.

Alternatively, we can also use the merge function to merge the two maps, taking care of combining the nullable values properly. The lambda function provided to the merge function checks if the existing value is null and returns the new value if it is, ensuring that we don't lose any nullable values during the merge.