Here's an approach:
import java.util.*;
public class Test
{
public static void main(String[] args)
{
List<Integer>list = new ArrayList<Integer>();
Collections.addAll(list, 1, 100, 2, 100, 3, 100);
List<Integer>singleton = Collections.singletonList(100);
List<Integer>copy = new ArrayList<Integer>(list);
copy.retainAll(singleton);
for(Integer n : copy)
{
System.out.println(n);
}
}
}