Jmeter Beanshell: Accessing global lists of data - scripting

Question

I'm using Jmeter to design a test that requires data to be randomly read from text files. To save memory, I have set up a "setUp Thread Group" with a BeanShell PreProcessor with the following:
//Imports
import org.apache.commons.io.FileUtils;
//Read data files
List items = FileUtils.readLines(new File(vars.get("DataFolder") + "/items.txt"));
//Store for future use
props.put("items", items);
I then attempt to read this in my other thread groups and am trying to access a random line in my text files with something like this:
(props.get("items")).get(new Random().nextInt((props.get("items")).size()))
However, this throws a "Typed variable declaration" error and I think it's because the get() method returns an object and I'm trying to invoke size() on it, since it's really a List. I'm not sure what to do here. My ultimate goal is to define some lists of data once to be used globally in my test so my tests don't have to store this data themselves.
Does anyone have any thoughts as to what might be wrong?
EDIT
I've also tried defining the variables in the setUp thread group as follows:
bsh.shared.items = items;
And then using them as this:
(bsh.shared.items).get(new Random().nextInt((bsh.shared.items).size()))
But that fails with the error "Method size() not found in class'bsh.Primitive'".

Answer 1

You were very close, just add casting to List so the interpreter will know what's the expected object:
log.info(((List)props.get("items")).get(new Random().nextInt((props.get("items")).size())));

Answer 2

Be aware that since JMeter 3.1 it is recommended to use Groovy for any form of scripting as:
Groovy performance is much better
Groovy supports more modern Java features while with Beanshell you're stuck at Java 5 level
Groovy has a plenty of JDK enhancements, i.e. File.readLines() function
So kindly find Groovy solution below:
In the first Thread Group:
props.put('items', new File(vars.get('DataFolder') + '/items.txt').readLines()
In the second Thread Group:
def items = props.get('items')
def randomLine = items.get(new Random().nextInt(items.size))