Import modules like `import <module> as <alias>` in Powershell - powershell

Question

So here's what I'm trying to do - in Java, for instance, if I want to use an ArrayList<> in my program I just write
...
import java.util.ArrayList
...
And then from there on I can just write ArrayList<String> arr = new ArrayList<String>... etc.
Also, in Python I can, for instance, write something like
from numpy.random import randint
And again, in my program I can just write randint(something).
Is there an equivalent way of doing this in PowerShell? I'd like to use a System.Collections.ArrayList, but I can't find any syntax online.

Answer 1

Reference a namespace with a using namespace statement:
using namespace System.Collections
Then you can omit the namespace when creating a new object
$arr = New-Object ArrayList

Answer 2

You have to create New-Object forSystem.Collections.ArrayList :
$arr= New-Object System.Collections.ArrayList
The New-Object cmdlet creates an instance of a .NET Framework or COM
object.
After that you can use ArrayList methods :
$arr.Add('test')

Answer 3

I will throw this in just for fun. First, create a function:
function New-ArrayList{
New-Object System.Collections.ArrayList
}
Next create an alias:
New-Alias -Name al -Value New-ArrayList
Then use it:
$myArrayList = al

Answer 4

The best option is probably the one given by #laika, but you can also use Type Accelerators. These used to be easy to work with, but from PSv3, things were made a bit more difficult (probably to force you to use better techniques). Built-in accelerators include the standard .NET types such as int, string, DateTime, etc, and more obscure things such as System.Management.ManagementObject. You can get a full list like this:
[PsObject].Assembly.GetType("System.Management.Automation.TypeAccelerators")::Get
To create your own, do this:
[PsObject].Assembly.GetType("System.Management.Automation.TypeAccelerators")::Add('ArrayList',"System.Collections.ArrayList")
You can then use the new accelerator like this:
$arrayList = New-Object ArrayList
$arrayList.Add(1)
$arrayList.Add(2)
$arrayList.Add(3)
$arrayList
1
2
3
Note that these last only for the current session, so would need recreated everytime you wanted to use them.