Flex Actionscript GoodNess: AS equivalent of Java Hashmap / Hashtable

With Java being the my core language, it always puzzles me why is there is not good Hashtable functionality..

There are lot of equivalents though, but I still miss the Java Hashtable.

Here are the Options

1. Associative Arrays

   1: var params:Array = new Array()

   2: params.firstName = txName.text

   3: params.lastName = txLName.text

   4: displayValues(params)

   5:  

   6: public static const FIRST_NAME:String ="firstName"

   7: public static const LAST_NAME:String = "lastName"

   8: //Retreive values From Associative Array

   9: public function displayValues(params:Array):void{

  10:     var firstName:String = params[FIRST_NAME]

  11:     var lastName:String = params[LAST_NAME]

  12:     trace(firstName)

  13:     trace(lastName)

  14: }

2. flash.utils.Dictionary

   1: import flash.utils.Dictionary

   2:  

   3: //Set values to dictionary

   4: public function dictionaryDemo(fName:String, lName:String):void{

   5:     var aDict:Dictionary = new Dictionary()

   6:     aDict.firstName = fName

   7:     aDict.lastName = lName

   8:      displayValues(aDict)

   9: }

  10: public function displayValues(aDict:Dictionary):void{

  11:     trace(aDict.firstName)

  12:     trace(aDict.lastName)

  13:  

  14: //You can also iterate over a Dictionary

  15:     for (val in aDict) { 

  16:         trace ("KeyVal pair is " + val + " = " + aDict[val]); 

  17:     }

  18: }

  19:  

What do you guys think, which one is better Associative Arrays or Dictionary..

By default, I have observed that actionscript Object type behaves like dictionary.