/* package whatever; // don't place package name! */
 
import java.util.*;
import java.lang.*;
import java.io.*;
import java.util.stream.*;
 
/* 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
	{
		// your code goes here
        Set<String> set = new HashSet<>(Arrays.asList("A", "B", "C"));
        final List<String> result = set.stream().flatMap(x->set.stream().map(y->x+y)).collect(Collectors.toList());
        System.out.println(result);
	}
}

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