code: import scala.Tuple2;
  import scala.collection.concurrent.TrieMap;
  import scala.collection.immutable.HashSet;
  import scala.collection.mutable.ArrayBuffer;
  
  public class Collections {
  
  	public static void main(String[] args) {
  		ArrayBuffer<Integer> myarrlist = new ArrayBuffer<Integer>();
  		ArrayBuffer<Integer> myarrlist2 = new ArrayBuffer<Integer>(20);
  
  		myarrlist.$plus$eq(new Integer(42)); // $plus$eq is Scala += operator
  		myarrlist.$plus$eq(13); // to add an element.
  		myarrlist.$plus$eq(-1);
  
  		myarrlist2 = (ArrayBuffer<Integer>) myarrlist2.$minus(-1);
  
  		for (int i = 0; i < 10; i++)
  			myarrlist2.$plus$eq(i);
  
  		// loop through myarrlist to sum each entry
  		int sum = 0;
  		for (int i = 0; i < myarrlist2.size(); i++) {
  			sum += myarrlist2.apply(i);
  		}
  		System.out.println("List is: " + myarrlist2 + " with head: "
  				+ myarrlist2.head() + " sum is: " + sum);
  		System.out.println("Third element is: " + myarrlist2.apply$mcII$sp(2));
  
  		Tuple2<String, String> tuple = new Tuple2<String, String>("US",
  				"Washington");
  		System.out.println("Tuple2 is : " + tuple);
  
  		ArrayBuffer<Tuple2<String, String>> capList = new ArrayBuffer<Tuple2<String, String>>();
  		capList.$plus$eq(new Tuple2<String, String>("US", "Washington"));
  		capList.$plus$eq(new Tuple2<String, String>("France", "Paris"));
  		System.out.println(capList);
  
  		TrieMap<String, String> trieMap = new TrieMap<String, String>();
  		trieMap.put("US", "Washington");
  		trieMap.put("France", "Paris");
  
  		HashSet<Character> set = new HashSet<Character>();
  
  		ArrayBuffer<Tuple2<String, String>> capBuffer = new ArrayBuffer<Tuple2<String, String>>();
  		trieMap.put("US", "Washington");
  
  		System.out.println(trieMap);
  	}
  }
  