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  • [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
    }
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  • 原文地址:https://www.cnblogs.com/Answer1215/p/13815089.html
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