Kotlin HashMap: hashMapOf()

2024年8月29日 | 阅读 7 分钟

hashMapOf() 是 HashMap 类的一个函数。它返回一个包含指定内容的新 HashMap。它包含键值对形式的数据。HashMap 是一个可变集合，提供读写功能。

hashMapOf() 函数的语法

Kotlin HashMap 类的函数

函数	描述
open fun put(key: K, value: V): V?	将指定的键和值放入 map 中
open operator fun get(key: K): V?	返回指定键的值，如果 map 中不存在指定的键，则返回 null。
open fun containsKey(key: K): Boolean	如果 map 包含指定的键，则返回 true。
open fun containsValue(value: V): Boolean	如果 map 将一个或多个键映射到指定的值，则返回 true。
open fun clear()	从 map 中移除所有元素。
open fun remove(key: K): V?	从 map 中移除指定的键及其对应的值

Kotlin hashMapOf() 示例 1

HashMap 的 hashMapOf() 函数可以声明为不同的泛型类型，例如 hashMapOf<Int, String>()、hashMapOf<String, String>()、hashMapOf<Any, Any>() 等。

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("hobby", "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

Kotlin hashMapOf() 示例 2 - containsKey()

如果 containsKey() 函数在 HashMap 中包含指定的键，则返回 true，否则返回 false。

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("hobby", "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 = hobby , value = Playing
......stringMap.containsKey("name").......
true

Kotlin hashMapOf() 示例 3 - containsValue()

如果 containsValue() 函数在 HashMap 中包含指定的值，则返回 true，否则返回 false。

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("hobby", "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 = hobby , value = Playing
.......stringMap.containsValue("Delhi")......
true
false

Kotlin hashMapOf() 示例 4 - contains()

如果 contains() 函数在 HashMap 中包含指定的键，则返回 true，否则返回 false。

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("hobby", "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 = hobby , value = Playing
......stringMap.contains("city").......
true

Kotlin hashMapOf() 示例 5 - replace(key, value)

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

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("hobby", "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 = hobby , 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 = hobby , value = Playing

Kotlin hashMapOf() 示例 6 - replace(key, oldValue, newValue)

replace(key, oldValue, newValue) 函数用于将指定键处的现有旧值替换为新的指定值。如果 replace(key, newValue, oldValue) 函数用新值替换了旧值，则返回 true，否则返回 false。

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("hobby", "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 = hobby , 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 = hobby , value = Playing

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

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

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("hobby", "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 = hobby , value = Playing
.....stringMap.size........
4
.......stringMap.keys......
[city, name, department, hobby]

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

getValue() 函数返回 HashMap 中指定键的值。而 getOrDefault() 函数返回 HashMap 中指定键的对应值（如果存在），或者如果 HashMap 中不存在此类键，则返回提到的默认值。

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("hobby", "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 = hobby , value = Playing
.......stringMap.getValue("department")......
Development
.......stringMap.getOrDefault("name", "Default Value")......
Ashu

Kotlin hashMapOf() 示例 9 - remove(key)

remove(key) 函数用于移除指定的键及其对应的值。 remove(key) 函数返回移除的值。

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

Kotlin hashMapOf() 示例 10 - remove(key, value)

remove(key, value) 函数用于移除指定的键及其对应的值。如果 remove(key, value) 函数移除指定的键及其值，则返回 true，否则返回 false。

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("hobby", "Playing")

    println("......traverse stringMap.......")
    for(key in stringMap.keys){
        println("Key = ${key} , value = ${stringMap[key]}")
    }
        println(".......stringMap.remove(\"hobby\",\"Playing\")......")
        println(stringMap.remove("hobby","Playing"))
    println("......traverse stringMap after stringMap.remove(\"hobby\",\"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 = hobby , value = Playing
.......stringMap.remove("hobby","Playing")......
true
......traverse stringMap after stringMap.remove("hobby","Playing").......
Key = city , value = Delhi
Key = name , value = Ashu
Key = department , value = Development

Kotlin hashMapOf() 示例 11 - set(key, value)

set(key, value) 函数用于在指定的键处设置给定的值（如果存在）。如果键在 HashMap 中不存在，它将添加新键并设置与该键对应的给定值。

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("hobby", "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 = hobby , 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 = hobby , value = Playing

Kotlin hashMapOf() 示例 12 - clear()

clear() 函数用于清除（或移除）HashMap 中的所有键值对。

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("hobby", "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 = hobby , value = Playing
......stringMap.clear().......
kotlin.Unit
{}

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Kotlin HashMap: hashMapOf()

hashMapOf() 函数的语法

Kotlin HashMap 类的函数

Kotlin hashMapOf() 示例 1

Kotlin hashMapOf() 示例 2 - containsKey()

Kotlin hashMapOf() 示例 3 - containsValue()

Kotlin hashMapOf() 示例 4 - contains()

Kotlin hashMapOf() 示例 5 - replace(key, value)

Kotlin hashMapOf() 示例 6 - replace(key, oldValue, newValue)

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

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

Kotlin hashMapOf() 示例 9 - remove(key)

Kotlin hashMapOf() 示例 10 - remove(key, value)

Kotlin hashMapOf() 示例 11 - set(key, value)

Kotlin hashMapOf() 示例 12 - clear()

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Kotlin HashMap: hashMapOf()

hashMapOf() 函数的语法

Kotlin HashMap 类的函数

Kotlin hashMapOf() 示例 1

Kotlin hashMapOf() 示例 2 - containsKey()

Kotlin hashMapOf() 示例 3 - containsValue()

Kotlin hashMapOf() 示例 4 - contains()

Kotlin hashMapOf() 示例 5 - replace(key, value)

Kotlin hashMapOf() 示例 6 - replace(key, oldValue, newValue)

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

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

Kotlin hashMapOf() 示例 9 - remove(key)

Kotlin hashMapOf() 示例 10 - remove(key, value)

Kotlin hashMapOf() 示例 11 - set(key, value)

Kotlin hashMapOf() 示例 12 - clear()

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