[Kotlin] Working with Map

fun main(args: Array<String>) {
    val namesToAges = mapOf(Pair("Peter", 24), Pair("Roger", 42))
    val namesToAges2 = mapOf(
        "Peter" to 24,
        "Roger" to 42
        )
    
        
    println(namesToAges == namesToAges2) // true
    
    println(namesToAges.keys) // [Peter, Roger]
    println(namesToAges.values) // [24, 42]
    println(namesToAges.entries) // [Peter=24, Roger=42]
    
    namesToAges.entries.forEach {
        println("${it.key} is ${it.value}")
    }
    /*
     * Peter is 24
       Roger is 42
     * */
    
    val countryToInhabitants = mutableMapOf(
        "Germany" to 80_000_000,
        "USA" to 300_000_000
    )
    countryToInhabitants.put("Australia", 23_000_000)
    countryToInhabitants.putIfAbsent("USA", 23_000_000) // "usa" already exists
    println(countryToInhabitants.contains("USA")) // true
    println(countryToInhabitants.containsKey("France")) // false
    println(countryToInhabitants.containsValue(20_000_000)) // false
    
    println(countryToInhabitants.get("Germany"))
    println(countryToInhabitants.getOrDefault("France", 0)) // 0
}