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CSC Interview Question: how to find common elements between two collections

Solution: retainAll method do this.   public boolean retainAll (Collection<?> c) Example: public class Test {        public static void main(String [] args){          LinkedHashSet hs = new LinkedHashSet();           // add elements to the hash set           hs.add("B");           hs.add("A");           hs.add("D");           hs.add("E");           hs.add("C");           hs.add("F");           System.out.println(hs);                     LinkedHashSet hs2 = new LinkedHashSet();           hs2.add("E");           hs2.add("C");           hs2.add("G");           System.out.println(hs2);           boolean retain=hs.retainAll(hs2);           System.out.println("retain:"+retain);           System.out.println(hs2);           System.out.println(hs);            } } ********************************************** Output: [B, A, D, E, C, F] [E, C, G] retain:true [E, C, G] [E, C]