Kotlin HashMap类

Kotlin HashMap是基于MutableMap接口的集合类。 Kotlin的HashMap类使用Hash表实现MutableMap接口。它以键和值对的形式存储数据。它表示为HashMap < key, value> 或HashMap < K, V> 。
HashMap类的实现不能保证键, 值和集合条目的数据顺序。
Kotlin HashMap类的构造方法

建设者 描述
HashMap() 构造一个空的HashMap实例
HashMap(initialCapacity:Int, loadFactor:Float = 0f) 它用于构造指定容量的HashMap。
HashMap(原始:Map < out K, V> ) 它构造一个HashMap实例, 其中填充了指定原始地图的内容。
Kotlin HashMap类的功能
功能 描述
打开趣味看跌期权(键:K, 值:V):V? 它将指定的键和值放入地图中
打开运算符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。
打开乐趣containsKey(key:K):布尔值 如果map包含指定键, 则返回true。
打开乐趣containsValue(value:V):布尔值 如果map将多个键之一映射到指定值, 则返回true。
open fun clear() 它从地图中删除所有元素。
打开乐趣删除(键:K):V? 它从映射中删除指定的键及其对应的值
Kotlin HashMap示例1-空HashMap
让我们创建一个简单的HashMap类定义示例, 该类使用< Int, String> 的空HashMap定义并稍后添加元素。要打印HashMap的值, 我们将使用HashMap [key]或HashMap.get(key)。
fun main(args: Array< String> ){val hashMap:HashMap< Int, String> = HashMap< Int, String> () //define empty hashmaphashMap.put(1, "Ajay")hashMap.put(3, "Vijay")hashMap.put(4, "Praveen")hashMap.put(2, "Ajay")println(".....traversing hashmap.......")for(key in hashMap.keys){println("Element at key $key = ${hashMap[key]}")}}

输出:
.....traversing hashmap.......Element at key 1 = AjayElement at key 2 = AjayElement at key 3 = VijayElement at key 4 = Praveen

Kotlin HashMap示例2- HashMap的初始容量
HashMap也可以使用其初始容量进行初始化。可以通过添加和替换其元素来更改容量。
fun main(args: Array< String> ){val hashMap:HashMap< String, String> = HashMap< String, String> (3)hashMap.put("name", "Ajay")hashMap.put("city", "Delhi")hashMap.put("department", "Software Development")println(".....traversing hashmap.......")for(key in hashMap.keys){println("Element at key $key = ${hashMap[key]}")}println(".....hashMap.size.......")println(hashMap.size)hashMap.put("hobby", "Travelling")println(".....hashMap.sizeafter adding hobby.......")println(hashMap.size)println(".....traversing hashmap.......")for(key in hashMap.keys){println("Element at key $key = ${hashMap.get(key)}")}}

【Kotlin HashMap类】输出:
.....traversing hashmap.......Element at key name = AjayElement at key department = Software DevelopmentElement at key city = Delhi.....hashMap.size.......3.....hashMap.sizeafter adding hobby.......4.....traversing hashmap.......Element at key name = AjayElement at key department = Software DevelopmentElement at key city = DelhiElement at key hobby = Travelling

Kotlin HashMap示例3- remove()和put()
函数remove()用于将指定键处的现有值替换为指定值。 put()函数在指定的键处添加一个新值, 并替换旧值。如果put()函数未找到任何指定的键, 它将在指定的键处放置一个新值。
fun main(args: Array< String> ){val hashMap:HashMap< Int, String> = HashMap< Int, String> ()hashMap.put(1, "Ajay")hashMap.put(3, "Vijay")hashMap.put(4, "Prakash")hashMap.put(2, "Rohan")println(".....traversing hashmap.......")for(key in hashMap.keys){println("Element at key $key = ${hashMap[key]}")}hashMap.replace(3, "Ashu")hashMap.put(2, "Raj")println(".....hashMap.replace(3, \"Ashu\")... hashMap.replace(2, \"Raj\").......")....")for(key in hashMap.keys){println("Element at key $key = ${hashMap[key]}")}}

输出:
.....traversing hashmap.......Element at key 1 = AjayElement at key 2 = RohanElement at key 3 = VijayElement at key 4 = Prakash.....hashMap.replace(3, "Ashu")...hashMap.put(2, "Raj")....Element at key 1 = AjayElement at key 2 = RajElement at key 3 = AshuElement at key 4 = Prakash

Kotlin HashMap示例4-containsKey(key)和containsValue(value)
如果HashMap中存在指定的键, 则函数containsKey()返回true;如果不存在此键, 则返回false。
函数containsValue()用于检查指定的值是否存在于HashMap中。如果HashMap中存在value, 它将返回true, 否则返回false。
fun main(args: Array< String> ){val hashMap:HashMap< Int, String> = HashMap< Int, String> ()hashMap.put(1, "Ajay")hashMap.put(3, "Vijay")hashMap.put(4, "Prakash")hashMap.put(2, "Rohan")println(".....traversing hashmap.......")for(key in hashMap.keys){println("Element at key $key = ${hashMap[key]}")}println(".....hashMap.containsKey(3).......")println(hashMap.containsKey(3))println(".....hashMap.containsValue(\"Rohan\").......")println(hashMap.containsValue("Rohan"))}

输出:
.....traversing hashmap.......Element at key 1 = AjayElement at key 2 = RohanElement at key 3 = VijayElement at key 4 = Prakash.....hashMap.containsKey(3).......true.....hashMap.containsValue("Rohan").......true

Kotlin HashMap示例5-clear()
clear()函数用于清除HashMap中的所有数据。
fun main(args: Array< String> ){val hashMap:HashMap< Int, String> = HashMap< Int, String> ()hashMap.put(1, "Ajay")hashMap.put(3, "Vijay")hashMap.put(4, "Prakash")hashMap.put(2, "Rohan")println(".....traversing hashmap.......")for(key in hashMap.keys){println("Element at key $key = ${hashMap[key]}")}println(".....hashMap.clear().......")hashMap.clear()println(".....print hashMap after clear().......")println(hashMap)}

输出:
.....traversing hashmap.......Element at key 1 = AjayElement at key 2 = RohanElement at key 3 = VijayElement at key 4 = Prakash.....hashMap.clear()............print hashMap after clear().......{}

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