📅  最后修改于: 2020-11-02 04:30:40             🧑  作者: Mango
Scala映射是键/值对的集合。可以根据其键检索任何值。键在地图中是唯一的,但值不必是唯一的。 HashMap实现不可变的映射,并使用哈希表实现相同的映射。
以下是用于声明HashMap变量的语法。
val colors = HashMap("red" -> "#FF0000", "azure" -> "#F0FFFF", "peru" -> "#CD853F")
在这里,颜色被声明为Strings,Int的哈希映射,它具有三个键值对。可以使用以下命令添加值-
var myMap1: HashMap[Char, Int] = colors + ("black" -> "#000000");
下面是一个示例程序,显示了如何创建,初始化和处理HashMap-
import scala.collection.immutable.HashMap
object Demo {
def main(args: Array[String]) = {
var myMap: HashMap[String,String] = HashMap(
"red" -> "#FF0000", "azure" -> "#F0FFFF", "peru" -> "#CD853F"
);
// Add an element
var myMap1: HashMap[String,String] = myMap + ("white" -> "#FFFFFF");
// Print key values
myMap.keys.foreach{
i =>
print( "Key = " + i )
println(" Value = " + myMap(i) )
}
if( myMap.contains( "red" )) {
println("Red key exists with value :" + myMap("red"))
} else {
println("Red key does not exist")
}
if( myMap.contains( "maroon" )) {
println("Maroon key exists with value :" + myMap("maroon"))
} else {
println("Maroon key does not exist")
}
//removing element
var myMap2: HashMap[String,String] = myMap - ("white");
// Create empty map
var myMap3: HashMap[String,String] = HashMap.empty[String, String];
println(myMap1);
println(myMap2);
println(myMap3);
}
}
将以上程序保存在Demo.scala中。以下命令用于编译和执行该程序。
\>scalac Demo.scala
\>scala Demo
Key = azure Value = #F0FFFF
Key = peru Value = #CD853F
Key = red Value = #FF0000
Red key exists with value :#FF0000
Maroon key does not exist
HashMap(azure -> #F0FFFF, peru -> #CD853F, white -> #FFFFFF, red -> #FF0000)
HashMap(azure -> #F0FFFF, peru -> #CD853F, red -> #FF0000)
HashMap()