/* package whatever; // don't place package name! */
 
import java.util.*;
import java.util.stream.Collectors;
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
	{
		List<String> list = Arrays.asList("a", "b", "c");
		String result = list.stream().map(s -> String.format("(?:%s)", s)).collect(Collectors.joining("|"));
		System.out.println(result);
	}
}

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