Kotlin - HashMapOf()

Kotlin - HashMapOf() 首页 / Kotlin入门教程 / Kotlin - HashMapOf()

hashMapOf()是HashMap类的函数。它返回一个具有指定内容的新HashMap。它包含键和值形式的数据对。 HashMap是可变集合，可提供读写函数。

hashMapOf()语法

inline fun <K, V> hashMapOf(): HashMap<K, V> (source)
fun <K, V> hashMapOf(vararg pairs: Pair<K, V>): HashMap<K, V> (source)

HashMap函数

FunctionDescription
open fun put(key: K, value: V): V?它将指定的键和值放在map中
open operator fun get(key: K): V?它返回指定键的值；如果map中没有这样的指定键，则返回null。
open fun containsKey(key: K): Boolean如果map包含指定键，则返回true。
open fun containsValue(value: V): Boolean如果map将多个键之一映射到指定值，则返回true。
open fun clear()它将所有元素从map中删除。
open fun remove(key: K): V?它从映射中删除指定的键及其对应的值

示例1

HashMap的hashMapOf()函数可以声明为不同的通用类型，例如hashMapOf <Int，String>()，hashMapOf <String，String>()，hashMapOf <Any，Any>()等。

复制代码
fun main(args: Array<String>){

    val intMap: HashMap<Int, String> = hashMapOf<Int,String>(1 to "Ashu",4 to "Rohan", 2 to "Ajeet", 3 to "Vijay")

    val stringMap: HashMap<String,String> = hashMapOf<String,String>("name" to "Ashu")
    stringMap.put("city", "Delhi")
    stringMap.put("department", "Development")
    stringMap.put("Learnfk", "Playing")
    val anyMap: HashMap<Any, Any> = hashMapOf<Any, Any>(1 to "Ashu", "name" to "Rohsan", 2 to 200)
    println(".....traverse intMap........")
    for(key in intMap.keys){
        println(intMap[key])
    }
    println("......traverse stringMap.......")
    for(key in stringMap.keys){
        println(stringMap[key])
    }
    println("......traverse anyMap.......")
    for(key in anyMap.keys){
        println(anyMap[key])
    }
}

输出:

.....traverse intMap........
Ashu
Ajeet
Vijay
Rohan
......traverse stringMap.......
Ashu
Development
Delhi
Playing
......traverse anyMap.......
Rohsan
Ashu
200

示例2 - containsKey()

如果它包含HashMap中的提及键，则包含keeryKey()函数返回true，否则返回false。

复制代码
fun main(args: Array<String>){

    val stringMap: HashMap<String,String> = hashMapOf<String,String>()
    stringMap.put("name", "Ashu")
    stringMap.put("city", "Delhi")
    stringMap.put("department", "Development")
    stringMap.put("Learnfk", "Playing")

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

    println("......stringMap.containsKey(\"name\").......")
    println(stringMap.containsKey("name"))
}

输出:

......traverse stringMap.......
Key = city , value = Delhi
Key = name , value = Ashu
Key = department , value = Development
Key = Learnfk , value = Playing
......stringMap.containsKey("name").......
true

示例3 - containtValue()

如果它包含HashMap中的提到值，则包含Value()函数返回true，否则返回false。

复制代码
fun main(args: Array<String>){

    val stringMap: HashMap<String,String> = hashMapOf<String,String>()
    stringMap.put("name", "Ashu")
    stringMap.put("city", "Delhi")
    stringMap.put("department", "Development")
    stringMap.put("Learnfk", "Playing")

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

    println(".......stringMap.containsValue(\"Delhi\")......")
    println(stringMap.containsValue("Delhi"))
    println(stringMap.containsValue("Mumbai"))
}

输出:

......traverse stringMap.......
Key = city , value = Delhi
Key = name , value = Ashu
Key = department , value = Development
Key = Learnfk , value = Playing
.......stringMap.containsValue("Delhi")......
true
false

示例4 - contains()

如果contains()函数在HashMap中包含提及键，则返回true，否则返回false。

复制代码
fun main(args: Array<String>){

    val stringMap: HashMap<String,String> = hashMapOf<String,String>()
    stringMap.put("name", "Ashu")
    stringMap.put("city", "Delhi")
    stringMap.put("department", "Development")
    stringMap.put("Learnfk", "Playing")

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

    println("......stringMap.contains(\"city\").......")
    println(stringMap.contains("city"))
}

输出:

......traverse stringMap.......
Key = city , value = Delhi
Key = name , value = Ashu
Key = department , value = Development
Key = Learnfk , value = Playing
......stringMap.contains("city").......
true

示例5 - replace(key, value)

replace(key，value)函数用于用新的指定值替换指定键处的现有值。 replace(key，value)函数返回替换后的值。

复制代码
fun main(args: Array<String>){

    val stringMap: HashMap<String,String> = hashMapOf<String,String>()
    stringMap.put("name", "Ashu")
    stringMap.put("city", "Delhi")
    stringMap.put("department", "Development")
    stringMap.put("Learnfk", "Playing")

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

    println("......stringMap.replace(\"city\",\"Mumbai\").......")
    println(stringMap.replace("city","Mumbai"))
    println("......traverse stringMap after stringMap.replace(\"city\",\"Mumbai\").......")
    for(key in stringMap.keys){
        println("Key = ${key} , value = ${stringMap[key]}")
    }
}

输出:

......traverse stringMap.......
Key = city , value = Delhi
Key = name , value = Ashu
Key = department , value = Development
Key = Learnfk , value = Playing
......stringMap.replace("city","Mumbai").......
Delhi
......traverse stringMap after stringMap.replace("city","Mumbai").......
Key = city , value = Mumbai
Key = name , value = Ashu
Key = department , value = Development
Key = Learnfk , value = Playing

示例6 - replace(key, oldValue, newValue)

replace(key，oldValue，newValue)函数用于用新的指定值替换指定键处的现有旧值。如果将旧值替换为新值，则replace(key，newValue，oldValue)函数返回true，否则返回false。

复制代码
fun main(args: Array<String>){

    val stringMap: HashMap<String,String> = hashMapOf<String,String>()
    stringMap.put("name", "Ashu")
    stringMap.put("city", "Delhi")
    stringMap.put("department", "Development")
    stringMap.put("Learnfk", "Playing")

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

    println(".......stringMap.replace(\"department\", \"Development\",\"Management\")......")
    println(stringMap.replace("department", "Development","Management"))
    println("......traverse stringMap after stringMap.replace(\"department\", \"Development\",\"Management\").......")
    for(key in stringMap.keys){
        println("Key = ${key} , value = ${stringMap[key]}")
    }
}

输出:

......traverse stringMap.......
Key = city , value = Delhi
Key = name , value = Ashu
Key = department , value = Development
Key = Learnfk , value = Playing
.......stringMap.replace("department", "Development","Management")......
true
......traverse stringMap after stringMap.replace("department", "Development","Management").......
Key = city , value = Delhi
Key = name , value = Ashu
Key = department , value = Management
Key = Learnfk , value = Playing

示例7 - hashMapOf().size, hashMapOf().key

hashMapOf()函数的size属性返回HashMap的总大小，而key属性返回HashMap的所有键。

复制代码
fun main(args: Array<String>){

    val stringMap: HashMap<String,String> = hashMapOf<String,String>()
    stringMap.put("name", "Ashu")
    stringMap.put("city", "Delhi")
    stringMap.put("department", "Development")
    stringMap.put("Learnfk", "Playing")

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

    println(".....stringMap.size........")
    println(stringMap.size)

    println(".......stringMap.keys......")
    println(stringMap.keys)
}

输出:

......traverse stringMap.......
Key = city , value = Delhi
Key = name , value = Ashu
Key = department , value = Development
Key = Learnfk , value = Playing
.....stringMap.size........
4
.......stringMap.keys......
[city, name, department, Learnfk]

示例8 - getValue(key), getOrDefault(key, defaultValue)

getValue()函数返回HashMap的指定键的值。如果getOrDefault()函数返回指定键的对应值(如果该键存在于HashMap中)，则返回指定的默认值(如果该键不存在于HashMap中)。

复制代码
fun main(args: Array<String>){

    val stringMap: HashMap<String,String> = hashMapOf<String,String>()
    stringMap.put("name", "Ashu")
    stringMap.put("city", "Delhi")
    stringMap.put("department", "Development")
    stringMap.put("Learnfk", "Playing")

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

    println(".......stringMap.getValue(\"department\")......")
    println(stringMap.getValue("department"))

    println(".......stringMap.getOrDefault(\"name\", \"Default Value\")......")
    println(stringMap.getOrDefault("name", "Default Value"))
}

输出:

......traverse stringMap.......
Key = city , value = Delhi
Key = name , value = Ashu
Key = department , value = Development
Key = Learnfk , value = Playing
.......stringMap.getValue("department")......
Development
.......stringMap.getOrDefault("name", "Default Value")......
Ashu

示例9 - remove(key)

remove(key)函数用于删除指定的键以及其对应的值。 remove(key)函数返回删除的值。

复制代码
fun main(args: Array<String>){

    val stringMap: HashMap<String,String> = hashMapOf<String,String>()
    stringMap.put("name", "Ashu")
    stringMap.put("city", "Delhi")
    stringMap.put("department", "Development")
    stringMap.put("Learnfk", "Playing")

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

        println("......stringMap.remove(\"city\").......")
        println(stringMap.remove("city"))
        println("......traverse stringMap after stringMap.remove(\"city\").......")
        for(key in stringMap.keys){
        println("Key = ${key} , value = ${stringMap[key]}")
    }
}

输出:

......traverse stringMap.......
Key = city , value = Delhi
Key = name , value = Ashu
Key = department , value = Development
Key = Learnfk , value = Playing
......stringMap.remove("city").......
Delhi
......traverse stringMap after stringMap.remove("city").......
Key = name , value = Ashu
Key = department , value = Development
Key = Learnfk , value = Playing

例10 - remove(key, value)

remove(key，value)函数用于删除指定的键及其对应的值。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。

复制代码
fun main(args: Array<String>){

    val stringMap: HashMap<String,String> = hashMapOf<String,String>()
    stringMap.put("name", "Ashu")
    stringMap.put("city", "Delhi")
    stringMap.put("department", "Development")
    stringMap.put("Learnfk", "Playing")

    println("......traverse stringMap.......")
    for(key in stringMap.keys){
        println("Key = ${key} , value = ${stringMap[key]}")
    }
        println(".......stringMap.remove(\"Learnfk\",\"Playing\")......")
        println(stringMap.remove("Learnfk","Playing"))
    println("......traverse stringMap after stringMap.remove(\"Learnfk\",\"Playing\").......")
    for(key in stringMap.keys){
        println("Key = ${key} , value = ${stringMap[key]}")
    }
}

输出:

......traverse stringMap.......
Key = city , value = Delhi
Key = name , value = Ashu
Key = department , value = Development
Key = Learnfk , value = Playing
.......stringMap.remove("Learnfk","Playing")......
true
......traverse stringMap after stringMap.remove("Learnfk","Playing").......
Key = city , value = Delhi
Key = name , value = Ashu
Key = department , value = Development

例11 - set(key, value)

set(key，value)函数用于设置给定键处的给定值(如果存在)。如果该key在HashMap中不存在，它将添加新key设置与之对应的给定值。

复制代码
fun main(args: Array<String>){

    val stringMap: HashMap<String,String> = hashMapOf<String,String>()
    stringMap.put("name", "Ashu")
    stringMap.put("city", "Delhi")
    stringMap.put("department", "Development")
    stringMap.put("Learnfk", "Playing")

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

    stringMap.set("name","Ashutosh")
    stringMap.set("skill","Kotlin")
    println("......traverse stringMap after stringMap.set(\"name\",\"Ashutosh\") and   stringMap.set(\"skill\",\"Kotlin\").......")
    for(key in stringMap.keys){
        println("Key = ${key} , value = ${stringMap[key]}")
    }
}

输出:

......traverse stringMap.......
Key = city , value = Delhi
Key = name , value = Ashu
Key = department , value = Development
Key = Learnfk , value = Playing
......stringMap.set("name","Ashutosh").......
......traverse stringMap after stringMap.set("name","Ashutosh") and stringMap.set("skill","Kotlin").......
Key = city , value = Delhi
Key = skill , value = Kotlin
Key = name , value = Ashutosh
Key = department , value = Development
Key = Learnfk , value = Playing

例12 - clear()

clear()函数用于清除从HashMap清除所有键值对。

复制代码
fun main(args: Array<String>){

    val stringMap: HashMap<String,String> = hashMapOf<String,String>()
    stringMap.put("name", "Ashu")
    stringMap.put("city", "Delhi")
    stringMap.put("department", "Development")
    stringMap.put("Learnfk", "Playing")

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

        println("......stringMap.clear().......")
        println(stringMap.clear())
        println(stringMap)

}

输出:

......traverse stringMap.......
Key = city , value = Delhi
Key = name , value = Ashu
Key = department , value = Development
Key = Learnfk , value = Playing
......stringMap.clear().......
kotlin.Unit
{}

祝学习愉快！(内容编辑有误？请选中要编辑内容 -> 右键 -> 修改 -> 提交！)

技术教程推荐

程序员进阶攻略 -〔胡峰〕

面试现场 -〔白海飞〕

许式伟的架构课 -〔许式伟〕

Swift核心技术与实战 -〔张杰〕

互联网人的英语私教课 -〔陈亦峰〕

实用密码学 -〔范学雷〕

大厂广告产品心法 -〔郭谊〕

自动化测试高手课 -〔柳胜〕

徐昊 · TDD项目实战70讲 -〔徐昊〕

好记忆不如烂笔头。留下您的足迹吧 :)
休闲君评测 |  TOOLFK工具网 |  chrome插件网 |  古诗文网 |  良许Linux教程网 |  Python之禅 |  红色石头 |  豪评测 |  入党申请书 | 

© 2020 Hi LearnFk 意见反馈 免责声明 关于我们 桂ICP备11002319号-3 友链&广告位+QQ: 1963612630