Kotlin MutableMap是集合框架的接口, 该集合以键和值对的形式保存对象。 MutableMap接口的值通过使用其对应的键来检索。键和值可以是不同的对, 例如< Int, Int> , < Int, String> , < Char, String> 等。MutableMap的每个键仅包含一个值。
要使用MutableMap接口, 我们需要使用其名为mutableMapOf()或mutableMapOf < k, v> ()的函数。
Kotlin MutableMap接口声明

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

MutableMap的属性

物产	描述
抽象val条目：MutableSet < MutableEntry < K, V > >	这将返回映射中所有键和值对的MutableSet。
抽象val键：MutableSet < K>	这将返回此映射中MutableSet的所有键。
抽象val值：MutableCollection < V>	这将返回当前映射中MutableCollection的所有值。此集合可能包含重复的值。

Kotlin MutableMap的功能

功能	描述
抽象有趣的put（key：K, value：V）：V？	它将给定值与映射中的指定键相加。
抽象乐趣putAll（来自：Map < out K, V> ）	这将使用上述映射中的键/值对更新当前映射。
抽象乐趣remove（key：K）：V？	它将指定的键及其对应的值从映射中删除。
open fun remove（key：K, value：V）：布尔值	仅当键和值实体存在于映射中时, 它才会从映射中删除。
abstract fun clear()	此功能用于从地图上删除所有元素。
运算符fun < K, V> Map < out K, V> .contains（key：K）：布尔值	它检查地图中的给定键。
抽象乐趣containsKey（key：K）：布尔	如果map包含指定的键, 则返回true。
fun < K> Map < out K, *> 。containsKey（key：K）：布尔值	如果map包含指定的键, 则返回true。
抽象乐趣containsValue（value：V）：布尔	如果地图为给定值映射一个或多个键, 则返回true。
fun < K, V> 映射< K, V> .containsValue（value：V）：布尔值	如果地图为给定值映射一个或多个键, 则返回true。
fun < K, V> 映射< out K, V> .count()：Int	它返回地图的实体总数
运算符fun < K, V> 映射< out K, V> .get（key：K）：V？	它返回对应于提及键的值；如果在地图中找不到这样的键, 则返回null。
fun < K, V> 映射< out K, V> .getOrDefault（key：K, defaultValue：V）：V	它返回带有相应提及键的值, 或者如果映射中没有针对键的此类映射, 则返回默认值。
fun < K, V> 映射< K, V> .getOrElse（键：K, defaultValue：()-> V）：V	它返回映射中提及键的值, 或者如果找不到给定键的此类条目, 则返回默认值函数。
有趣的< K, V> 映射< K, V> .getValue（key：K）：V	它返回与给定键对应的值, 如果在映射中找不到键, 则抛出异常。

Kotlin MutableMap示例-遍历1个MutableMap
让我们创建一个示例, 使用mutablemapOf()函数创建一个MutableMap并遍历它。在此示例中, 我们以不同的方式创建了MutableMap的三种不同类型（MutableMap < Int, String> , MutableMap < String, String> 和MutableMap < Any, Any> ）。

fun main(args: Array< String> ) {val mutableMap1: MutableMap< Int, String> = mutableMapOf< Int, String> (1 to "Ashu", 4 to "Rohan", 2 to "Ajeet", 3 to "Vijay")val mutableMap2: MutableMap< String, String> = mutableMapOf< String, String> ()mutableMap2.put("name", "Ashu")mutableMap2.put("city", "Delhi")mutableMap2.put("department", "Development")mutableMap2.put("hobby", "Playing")val mutableMap3: MutableMap< Any, Any> = mutableMapOf< Any, Any> (1 to "Ashu", "name" to "Rohsan", 2 to 200)println(".....traverse mutableMap1........")for (key in mutableMap1.keys) {println("Key = ${key}, Value = http://www.srcmini.com/${mutableMap1[key]}")}println("......traverse mutableMap2.......")for (key in mutableMap2.keys) {println("Key = "+key +", "+"Value = "http://www.srcmini.com/+mutableMap2[key])}println("......traverse mutableMap3......")for (key in mutableMap3.keys) {println("Key = ${key}, Value = http://www.srcmini.com/${mutableMap3[key]}")}}

输出：

.....traverse mutableMap1........Key = 1, Value = http://www.srcmini.com/AshuKey = 4, Value = RohanKey = 2, Value = AjeetKey = 3, Value = Vijay......traverse mutableMap2.......Key = name, Value = AshuKey = city, Value = DelhiKey = department, Value = DevelopmentKey = hobby, Value = Playing......traverse mutableMap3......Key = 1, Value = AshuKey = name, Value = RohsanKey = 2, Value = 200

Kotlin MutableMap示例-2 put()和putAll()
函数put()和putAll()用于在MutableMap中添加元素。 put()函数一次添加单个元素, 而putAll()函数在MutableMap中添加集合类型元素。例如：

fun main(args: Array< String> ) {val mutableMap: MutableMap< String, String> = mutableMapOf< String, String> ()mutableMap.put("name", "Ashu")mutableMap.put("city", "Delhi")val hashMap: HashMap< String, String> = hashMapOf< String, String> ()hashMap.put("department", "Development")hashMap.put("hobby", "Playing")println("......traverse mutableMap.......")for (key in mutableMap.keys) {println("Key = "+key +", "+"Value = "http://www.srcmini.com/+mutableMap[key])}mutableMap.putAll(hashMap)println("......traverse mutableMap after mutableMap.putAll(hashMap).......")for (key in mutableMap.keys) {println("Key = "+key +", "+"Value = "http://www.srcmini.com/+mutableMap[key])}}

输出：

......traverse mutableMap.......Key = name, Value = http://www.srcmini.com/AshuKey = city, Value = Delhi......traverse mutableMap after mutableMap.putAll(hashMap).......Key = name, Value = AshuKey = city, Value = DelhiKey = department, Value = DevelopmentKey = hobby, Value = Playing

Kotlin MutableMap示例-3 containsKey()
containsKey()函数用于检查指定的键是否在MutableMap中存在。如果包含指定的键, 则返回true, 否则返回false。例如：

fun main(args: Array< String> ) {val mutableMap: MutableMap< String, String> = mutableMapOf< String, String> ()mutableMap.put("name", "Ashu")mutableMap.put("city", "Delhi")mutableMap.put("department", "Development")mutableMap.put("hobby", "Playing")println("......traverse mutableMap.......")for (key in mutableMap.keys) {println("Key = "+key +", "+"Value = "http://www.srcmini.com/+mutableMap[key])}println("......mutableMap.containsKey(\"city\").......")println(mutableMap.containsKey("city"))}

输出：

......traverse mutableMap.......Key = name, Value = http://www.srcmini.com/AshuKey = city, Value = DelhiKey = department, Value = DevelopmentKey = hobby, Value = Playing......mutableMap.containsKey("city").......true

Kotlin MutableMap示例-4 containsValue()
containsValue()函数用于检查指定的值是否存在于MutableMap中。如果映射映射给定值的一个或多个键, 则此函数返回true, 否则返回false。例如：

fun main(args: Array< String> ) {val mutableMap: MutableMap< String, String> = mutableMapOf< String, String> ()mutableMap.put("name", "Ashu")mutableMap.put("city", "Delhi")mutableMap.put("department", "Development")mutableMap.put("hobby", "Playing")println("......traverse mutableMap.......")for (key in mutableMap.keys) {println("Key = "+key +", "+"Value = "http://www.srcmini.com/+mutableMap[key])}println(".......mutableMap.containsValue(\"Delhi\")......")println(mutableMap.containsValue("Delhi"))println(".......mutableMap.containsValue(\"Mumbai\")......")println(mutableMap.containsValue("Mumbai"))}

输出：

......traverse mutableMap.......Key = name, Value = http://www.srcmini.com/AshuKey = city, Value = DelhiKey = department, Value = DevelopmentKey = hobby, Value = Playing.......mutableMap.containsValue("Delhi")......true.......mutableMap.containsValue("Mumbai")......false

Kotlin MutableMap示例-5 contains()
contains()函数用于检查MutableMap中是否存在指定的键值。如果MutableMap中存在指定的键或值, 则它将返回true, 否则将返回false。例如：

fun main(args: Array< String> ) {val mutableMap: MutableMap< String, String> = mutableMapOf< String, String> ()mutableMap.put("name", "Ashu")mutableMap.put("city", "Delhi")mutableMap.put("department", "Development")mutableMap.put("hobby", "Playing")println("......traverse mutableMap.......")for (key in mutableMap.keys) {println("Key = "+key +", "+"Value = "http://www.srcmini.com/+mutableMap[key])}println("......mutableMap.contains(\"city\").......")println(mutableMap.contains("city"))}

输出：

......traverse mutableMap.......Key = name, Value = http://www.srcmini.com/AshuKey = city, Value = DelhiKey = department, Value = DevelopmentKey = hobby, Value = Playing......mutableMap.contains("city").......true

Kotlin MutableMap示例-6 get（key）
get（key）函数用于在MutableMap中检索指定键的对应值。如果MutableMap中不存在此类键, 则返回null。例如：

fun main(args: Array< String> ) {val mutableMap: MutableMap< String, String> = mutableMapOf< String, String> ()mutableMap.put("name", "Ashu")mutableMap.put("city", "Delhi")mutableMap.put("department", "Development")mutableMap.put("hobby", "Playing")println("......traverse mutableMap.......")for (key in mutableMap.keys) {println("Key = "+key +", "+"Value = "http://www.srcmini.com/+mutableMap[key])}println(".......mutableMap.get(\"department\")......")println(mutableMap.get("department"))}

输出：

......traverse mutableMap.......Key = name, Value = http://www.srcmini.com/AshuKey = city, Value = DelhiKey = department, Value = DevelopmentKey = hobby, Value = Playing.......mutableMap.get("department")......Development

Kotlin MutableMap示例-7 getValue（key）
用于返回MutableMap的指定键的对应值的getValue()函数, 或者如果在地图中找不到键, 则抛出异常。例如：

fun main(args: Array< String> ) {val mutableMap: MutableMap< String, String> = mutableMapOf< String, String> ()mutableMap.put("name", "Ashu")mutableMap.put("city", "Delhi")mutableMap.put("department", "Development")mutableMap.put("hobby", "Playing")println("......traverse mutableMap.......")for (key in mutableMap.keys) {println("Key = ${key}, Value = http://www.srcmini.com/${mutableMap[key]}")}println(".......mutableMap.getValue(\"department\")......")println(mutableMap.getValue("department"))}

输出：

......traverse mutableMap.......Key = name, Value = http://www.srcmini.com/AshuKey = city, Value = DelhiKey = department, Value = DevelopmentKey = hobby, Value = Playing.......mutableMap.getValue("department")......Development

Kotlin MutableMap示例-8 getOrDefault()
getOrDefault()函数返回MutableMap的指定键的对应值。如果MutableMap中不存在此类键, 则它将返回默认提及值。例如：

fun main(args: Array< String> ) {val mutableMap: MutableMap< String, String> = mutableMapOf< String, String> ()mutableMap.put("name", "Ashu")mutableMap.put("city", "Delhi")mutableMap.put("department", "Development")mutableMap.put("hobby", "Playing")println("......traverse mutableMap.......")for (key in mutableMap.keys) {println("Key = ${key}, Value = http://www.srcmini.com/${mutableMap[key]}")}println(".......mutableMap.getOrDefault(\"name\", \"Default Value\")......")println(mutableMap.getOrDefault("name", "default value"))}

输出：

......traverse mutableMap.......Key = name, Value = http://www.srcmini.com/AshuKey = city, Value = DelhiKey = department, Value = DevelopmentKey = hobby, Value = Playing.......mutableMap.getOrDefault("name", "Default Value")......Ashu

Kotlin MutableMap示例-9 count()
count()函数用于返回MutableMap中存在的元素总数。例如：

fun main(args: Array< String> ) {val mutableMap: MutableMap< String, String> = mutableMapOf< String, String> ()mutableMap.put("name", "Ashu")mutableMap.put("city", "Delhi")mutableMap.put("department", "Development")mutableMap.put("hobby", "Playing")println("......traverse mutableMap.......")for (key in mutableMap.keys) {println("Key = ${key}, Value = http://www.srcmini.com/${mutableMap[key]}")}println(".....mutableMap.count()........")println(mutableMap.count())}

输出：

......traverse mutableMap.......Key = name, Value = http://www.srcmini.com/AshuKey = city, Value = DelhiKey = department, Value = DevelopmentKey = hobby, Value = Playing.....mutableMap.count()........4

Kotlin MutableMap示例-10 remove（key）和remove（key, value）
remove（key）函数用于删除与其提及键相对应的值。而remove（key, value）函数删除包含键和值的元素。如果remove（key, value）函数将指定的键及其值一起移除, 则返回true, 否则返回false。例如：

fun main(args: Array< String> ) {val mutableMap: MutableMap< String, String> = mutableMapOf< String, String> ()mutableMap.put("name", "Ashu")mutableMap.put("city", "Delhi")mutableMap.put("department", "Development")mutableMap.put("hobby", "Playing")println("......traverse mutableMap.......")for (key in mutableMap.keys) {println("Key = ${key}, Value = http://www.srcmini.com/${mutableMap[key]}")}println("......mutableMap.remove(\"city\").......")println(mutableMap.remove("city"))println(".......mutableMap.remove(\"hobby\", \"Playing\")......")println(mutableMap.remove("hobby", "Playing"))println("......traverse mutableMap.......")for (key in mutableMap.keys) {println("Key = ${key}, Value = http://www.srcmini.com/${mutableMap[key]}")}}

输出：

......traverse mutableMap.......Key = name, Value = http://www.srcmini.com/AshuKey = city, Value = DelhiKey = department, Value = DevelopmentKey = hobby, Value = Playing......mutableMap.remove("city").......Delhi.......mutableMap.remove("hobby", "Playing")......true......traverse mutableMap after remove.......Key = name, Value = http://www.srcmini.com/AshuKey = department, Value = Development

Kotlin MutableMap示例-11 clear()
clear()函数用于从MutableMap中删除所有元素。例如：

fun main(args: Array< String> ) {val mutableMap: MutableMap< String, String> = mutableMapOf< String, String> ()mutableMap.put("name", "Ashu")mutableMap.put("city", "Delhi")mutableMap.put("department", "Development")mutableMap.put("hobby", "Playing")println("......traverse mutableMap.......")for (key in mutableMap.keys) {println("Key = ${key}, Value = http://www.srcmini.com/${mutableMap[key]}")}println("......mutableMap.clear().......")println(mutableMap.clear())println(mutableMap)}

【Kotlin MutableMap接口】输出：

......traverse mutableMap.......Key = name, Value = http://www.srcmini.com/AshuKey = city, Value = DelhiKey = department, Value = DevelopmentKey = hobby, Value = Playing......mutableMap.clear().......kotlin.Unit{}

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