/* package whatever; // don't place package name! */
 
import java.util.*;
import java.lang.*;
import java.io.*;
 
/* Name of the class has to be "Main" only if the class is public. */
class Ideone
{
	public static void main (String[] args) throws java.lang.Exception
	{
		 Map<String, List<Integer>> m = new HashMap<>();
		m.put("test", new ArrayList<Integer>(Arrays.asList(1,2,3)));
		m.put("test2", new ArrayList<Integer>(Arrays.asList(2,3,4)));
 
		List<Integer> flattenList = new ArrayList<>();
		for(List<Integer> list : m.values()){
			for(Integer i : list)
				flattenList.add(i);
		}
		System.out.println(flattenList);
	}
}

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