Kotlin MutableMap介面 - tw511教學網

Kotlin MutableMap是集合框架的介面，它以鍵和值對的形式儲存物件。通過使用相應的鍵來檢索MutableMap介面的值。鍵和值可以是不同型別的對，例如<Int，Int>，<Int，String>，<Char，String>等等。MutableMap的每個鍵只儲存一個值。

要使用MutableMap介面，我們需要使用它的函式：mutableMapOf()或mutableMapOf <k,v>()。

Kotlin MutableMap介面宣告

interface MutableMap<K, V> : Map<K, V> (source)

MutableMap屬性

屬性	描述
`MutableSet<MutableEntry<K, V>>`	這將返回對映中所有鍵和值對的`MutableSet`。
`MutableSet<K>`	這將返回此對映中`MutableSet`的所有鍵。
`MutableCollection<V>`	這將返回當前對映中`MutableCollection`的所有值。此集合可能包含重複值。

Kotlin MutableMap的函式

函式	描述
`abstract fun put(key: K, value: V): V?`	使用對映中的指定鍵新增給定值。
`abstract fun putAll(from: Map<out K, V>)`	使用指定對映中的鍵/值對更新當前對映。
`abstract fun remove(key: K): V?`	從對映中刪除指定的鍵及對應的值。
`open fun remove(key: K, value: V): Boolean`	僅當對映中存在鍵和值實體時，它才會從對映中刪除它們。
`abstract fun clear()`	此函式用於從對映中刪除所有元素。
`operator fun <K, V> Map<out K, V>.contains(key: K): Boolean`	它檢查對映中是否包含給定鍵。
`abstract fun containsKey(key: K): Boolean`	如果`map`包含指定的鍵，則返回`true`。
`fun <K> Map<out K, *>.containsKey(key: K): Boolean`	如果`map`包含指定的鍵，則返回`true`。
`abstract fun containsValue(value: V): Boolean`	如果對映包含給定值的一個或多個鍵，則返回`true`。
`fun <K, V> Map<K, V>.containsValue(value: V): Boolean`	如果對映包含給定值的一個或多個鍵，則返回`true`。
`fun <K, V> Map<out K, V>.count(): Int`	它返回對映的專案總數。
`operator fun <K, V> Map<out K, V>.get(key: K): V?`	它返回與鍵對應的值，如果在對映中找不到指定鍵，則返回`null`。
`fun <K, V> Map<out K, V>.getOrDefault(key: K, defaultValue: V): V`	它返回帶有相應指定鍵的值，或者如果對映中沒有鍵的對映，則返回預設值。
`fun <K, V> Map<K, V>.getOrElse(key: K, defaultValue: () -> V ): V`	它返回對映中提及鍵的值，或者如果找不到給定鍵的此類條目，則返回預設值函式。
`fun <K, V> Map<K, V>.getValue(key: K): V`	它返回與給定鍵對應的值，如果在對映中找不到鍵，則丟擲異常。

Kotlin MutableMap範例 - 1遍歷MutableMap

首先建立一個使用mutablemapOf()函式建立MutableMap並遍歷它的範例。在這個例子中，使用不同的方式(MutableMap <Int，String>，MutableMap <String，String>和MutableMap <Any，Any>)來建立MutableMap的三種不同型別。

fun main(args: Array<String>) {

    val mutableMap1: MutableMap<Int, String> = mutableMapOf<Int, String>(1 to "Java", 4 to "Ruby", 2 to "Ajax", 3 to "Vivi")
    val mutableMap2: MutableMap<String, String> = mutableMapOf<String, String>()
    mutableMap2.put("name", "Susen")
    mutableMap2.put("city", "海口")
    mutableMap2.put("department", "研發部")
    mutableMap2.put("hobby", "擼程式碼")
    val mutableMap3: MutableMap<Any, Any> = mutableMapOf<Any, Any>(1 to "Maxsu", "name" to "Ruby", 2 to 200)
    println(".....traverse mutableMap1........")
    for (key in mutableMap1.keys) {
        println("Key = ${key}, Value = ${mutableMap1[key]}")
    }
    println("......traverse mutableMap2.......")
    for (key in mutableMap2.keys) {
        println("Key = "+key +", "+"Value = "+mutableMap2[key])
    }
    println("......traverse mutableMap3......")
    for (key in mutableMap3.keys) {
        println("Key = ${key}, Value = ${mutableMap3[key]}")
    }
}

執行上面範例程式碼，得到以下結果 -

.....traverse mutableMap1........
Key = 1, Value = Java
Key = 4, Value = Ruby
Key = 2, Value = Ajax
Key = 3, Value = Vivi
......traverse mutableMap2.......
Key = name, Value = Susen
Key = city, Value = 海口
Key = department, Value = 研發部
Key = hobby, Value = 擼程式碼
......traverse mutableMap3......
Key = 1, Value = Maxsu
Key = name, Value = Ruby
Key = 2, Value = 200

Kotlin MutableMap範例2 - put()和putAll()函式

put()和putAll()函式用於新增MutableMap中的元素。put()函式向MutableMap中新增單個元素，putAll()函式向MutableMap新增集合型別元素。例如：

fun main(args: Array<String>) {

    val mutableMap: MutableMap<String, String> = mutableMapOf<String, String>()
    mutableMap.put("name", "Susen")
    mutableMap.put("city", "海口")

    val hashMap: HashMap<String,String> = hashMapOf<String,String>()
    hashMap.put("department", "研發部")
    hashMap.put("hobby", "擼程式碼")

    println("......traverse mutableMap.......")
    for (key in mutableMap.keys) {
        println("Key = "+key +", "+"Value = "+mutableMap[key])
    }
    mutableMap.putAll(hashMap)
    println("......traverse mutableMap after mutableMap.putAll(hashMap).......")
    for (key in mutableMap.keys) {
        println("Key = "+key +", "+"Value = "+mutableMap[key])
    }
}

執行上面範例程式碼，得到以下結果 -

......traverse mutableMap.......
Key = name, Value = Susen
Key = city, Value = 海口
......traverse mutableMap after mutableMap.putAll(hashMap).......
Key = name, Value = Susen
Key = city, Value = 海口
Key = department, Value = 研發部
Key = hobby, Value = 擼程式碼

Kotlin MutableMap範例3 - containsKey()函式

containsKey()函式用於檢查MutableMap中是否存在指定的鍵。如果它包含指定的鍵，則返回true，否則返回false。例如：

fun main(args: Array<String>) {

    val mutableMap: MutableMap<String, String> = mutableMapOf<String, String>()
    mutableMap.put("name", "Maxsu")
    mutableMap.put("city", "海口")
    mutableMap.put("department", "研發部")
    mutableMap.put("hobby", "女")

    println("......traverse mutableMap.......")

    for (key in mutableMap.keys) {
        println("Key = "+key +", "+"Value = "+mutableMap[key])
    }

    println("......mutableMap.containsKey(\"city\").......")
    println(mutableMap.containsKey("city"))
}

執行上面範例程式碼，得到以下結果 -

......traverse mutableMap.......
Key = name, Value = Maxsu
Key = city, Value = 海口
Key = department, Value = 研發部
Key = hobby, Value = 女
......mutableMap.containsKey("city").......
true

Kotlin MutableMap範例4 - containsValue()函式

containsValue()函式用於檢查MutableMap中是否存在指定的值。如果對映包含給定的一個或多個值，則此函式返回true，否則返回false。例如：

fun main(args: Array<String>) {

    val mutableMap: MutableMap<String, String> = mutableMapOf<String, String>()
    mutableMap.put("name", "Maxsu")
    mutableMap.put("city", "海口")
    mutableMap.put("department", "研發部")
    mutableMap.put("hobby", "擼程式碼")

    println("......traverse mutableMap.......")

    for (key in mutableMap.keys) {
        println("Key = "+key +", "+"Value = "+mutableMap[key])
    }

    println(".......mutableMap.containsValue(\"上海\")......")
    println(mutableMap.containsValue("上海"))
    println(".......mutableMap.containsValue(\"Maxsu\")......")
    println(mutableMap.containsValue("Maxsu"))
}

執行上面範例程式碼，得到以下結果 -

......traverse mutableMap.......
Key = name, Value = Maxsu
Key = city, Value = 海口
Key = department, Value = 研發部
Key = hobby, Value = 擼程式碼
.......mutableMap.containsValue("上海")......
false
.......mutableMap.containsValue("Maxsu")......
true

Kotlin MutableMap範例5 - contains()函式

contains()函式用於檢查MutableMap中是否存在指定的值鍵。如果指定的鍵或值存在於MutableMap中，則它將返回true，否則返回false。例如：

fun main(args: Array<String>) {

    val mutableMap: MutableMap<String, String> = mutableMapOf<String, String>()
    mutableMap.put("name", "Susen")
    mutableMap.put("city", "Haikou")
    mutableMap.put("department", "Development")
    mutableMap.put("hobby", "Coding")

    println("......traverse mutableMap.......")

    for (key in mutableMap.keys) {
        println("Key = "+key +", "+"Value = "+mutableMap[key])
    }

    println("......mutableMap.contains(\"city\").......")
    println(mutableMap.contains("city"))

}

執行上面範例程式碼，得到以下結果 -

......traverse mutableMap.......
Key = name, Value = Susen
Key = city, Value = Haikou
Key = department, Value = Development
Key = hobby, Value = Coding
......mutableMap.contains("city").......
true

Kotlin MutableMap範例6 - get(key)函式

get(key)函式用於檢索MutableMap中指定鍵的對應值。如果MutableMap中沒有包含指定鍵，則返回null。例如：

fun main(args: Array<String>) {

    val mutableMap: MutableMap<String, String> = mutableMapOf<String, String>()
    mutableMap.put("name", "Susen")
    mutableMap.put("city", "Haikou")
    mutableMap.put("department", "Development")
    mutableMap.put("hobby", "Coding")

    println("......traverse mutableMap.......")

    for (key in mutableMap.keys) {
        println("Key = "+key +", "+"Value = "+mutableMap[key])
    }

    println(".......mutableMap.get(\"department\")......")
    println(mutableMap.get("department"))

}

執行上面範例程式碼，得到以下結果 -

......traverse mutableMap.......
Key = name, Value = Susen
Key = city, Value = Haikou
Key = department, Value = Development
Key = hobby, Value = Coding
.......mutableMap.get("department")......
Development

Kotlin MutableMap範例7 - getValue(key)函式

getValue()函式用於返回MutableMap的指定鍵的相應值，如果在map中找不到鍵，則丟擲異常。例如：

fun main(args: Array<String>) {

    val mutableMap: MutableMap<String, String> = mutableMapOf<String, String>()
    mutableMap.put("name", "Maxsu")
    mutableMap.put("city", "海口")
    mutableMap.put("department", "Development")
    mutableMap.put("hobby", "擼程式碼")

    println("......traverse mutableMap.......")
    for (key in mutableMap.keys) {
        println("Key = ${key}, Value = ${mutableMap[key]}")
    }

    println(".......mutableMap.getValue(\"department\")......")
    println(mutableMap.getValue("department"))
}

執行上面範例程式碼，得到以下結果 -

......traverse mutableMap.......
Key = name, Value = Maxsu
Key = city, Value = 海口
Key = department, Value = Development
Key = hobby, Value = 擼程式碼
.......mutableMap.getValue("department")......
Development

Kotlin MutableMap範例8 - getOrDefault()函式

getOrDefault()函式返回MutableMap指定鍵的對應值。如果MutableMap中不存在指定的鍵，則返回預設對應值。例如：

fun main(args: Array<String>) {

    val mutableMap: MutableMap<String, String> = mutableMapOf<String, String>()
    mutableMap.put("name", "Maxsu")
    mutableMap.put("city", "海口")
    mutableMap.put("department", "Development")
    mutableMap.put("hobby", "擼程式碼")

    println("......traverse mutableMap.......")

    for (key in mutableMap.keys) {
        println("Key = ${key}, Value = ${mutableMap[key]}")
    }

    println(".......mutableMap.getOrDefault(\"name\", \"Default Value\")......")
    println(mutableMap.getOrDefault("name", "default-value"))

}

執行上面範例程式碼，得到以下結果 -

......traverse mutableMap.......
Key = name, Value = Maxsu
Key = city, Value = 海口
Key = department, Value = Development
Key = hobby, Value = 擼程式碼
.......mutableMap.getOrDefault("name", "Default Value")......
Maxsu

Kotlin MutableMap範例9 - count()函式

count()函式用於返回MutableMap中存在的元素總數。例如：

fun main(args: Array<String>) {

    val mutableMap: MutableMap<String, String> = mutableMapOf<String, String>()
    mutableMap.put("name", "Maxsu")
    mutableMap.put("city", "海口")
    mutableMap.put("department", "Development")
    mutableMap.put("hobby", "擼程式碼")
    println("......traverse mutableMap.......")

    for (key in mutableMap.keys) {
        println("Key = ${key}, Value = ${mutableMap[key]}")
    }

    println(".....mutableMap.count()........")
    println(mutableMap.count())
}

執行上面範例程式碼，得到以下結果 -

......traverse mutableMap.......
Key = name, Value = Maxsu
Key = city, Value = 海口
Key = department, Value = Development
Key = hobby, Value = 擼程式碼
.....mutableMap.count()........
4

Kotlin MutableMap範例10 - remove(key) 和 remove(key, value)函式

remove(key)函式用於刪除與指定鍵對應的值。而remove(key，value)函式刪除包含鍵和值的元素。如果成功刪除指定的鍵及其值，則remove(key，value)函式返回true，否則返回false。例如：

fun main(args: Array<String>) {

    val mutableMap: MutableMap<String, String> = mutableMapOf<String, String>()
    mutableMap.put("name", "Maxsu")
    mutableMap.put("city", "海口")
    mutableMap.put("department", "Development")
    mutableMap.put("hobby", "擼程式碼")
    println("......traverse mutableMap.......")

    for (key in mutableMap.keys) {
        println("Key = ${key}, Value = ${mutableMap[key]}")
    }

    println("......mutableMap.remove(\"city\").......")
    println(mutableMap.remove("city"))

    println(".......mutableMap.remove(\"hobby\",\"擼程式碼\")......")
    println(mutableMap.remove("hobby","擼程式碼"))

    println("......traverse mutableMap.......")
    for (key in mutableMap.keys) {
        println("Key = ${key}, Value = ${mutableMap[key]}")
    }
}

執行上面範例程式碼，得到以下結果 -

......traverse mutableMap.......
Key = name, Value = Maxsu
Key = city, Value = 海口
Key = department, Value = Development
Key = hobby, Value = 擼程式碼
......mutableMap.remove("city").......
海口
.......mutableMap.remove("hobby","擼程式碼")......
true
......traverse mutableMap.......
Key = name, Value = Maxsu
Key = department, Value = Development

Kotlin MutableMap範例11 - clear()函式

clear()函式用於從MutableMap中刪除所有元素。例如：

fun main(args: Array<String>) {

    val mutableMap: MutableMap<String, String> = mutableMapOf<String, String>()
    mutableMap.put("name", "Maxsu")
    mutableMap.put("city", "海口")
    mutableMap.put("department", "技術部")
    mutableMap.put("hobby", "擼程式碼")

    println("......traverse mutableMap.......")

    for (key in mutableMap.keys) {
        println("Key = ${key}, Value = ${mutableMap[key]}")
    }

    println("......mutableMap.clear().......")
    println(mutableMap.clear())
    println(mutableMap)
}

執行上面範例程式碼，得到以下結果 -

......traverse mutableMap.......
Key = name, Value = Maxsu
Key = city, Value = 海口
Key = department, Value = 技術部
Key = hobby, Value = 擼程式碼
......mutableMap.clear().......
kotlin.Unit
{}