MyTreeMap.java

import java.util.LinkedList;
import java.util.Iterator;
import tree.LinkedBinarySearchTree;

public class MyTreeMap{
  LinkedBinarySearchTree<Element> tree =
    new LinkedBinarySearchTree<Element>();

  public LinkedList<Integer> put(String key, Integer location){
    Element element = new Element(key, null);
    Element old = tree.find(element);
    if (old != null){
      LinkedList updated = old.getValue();
      updated.add(location);
      tree.addElement(new Element(key, updated));
      return old.getValue();
    }else{
      LinkedList<Integer> list = new LinkedList<Integer>();
      list.add(location);
      tree.addElement(new Element(key, list));
      return null;
    }
  }

  public LinkedList<Integer> get(String key){
     Element target = new Element(key, null);
     Element result = tree.find(target);
     if(result != null){
       return result.getValue();
     }else{
       return null;
     }
   }

  /**
   * Create an inorder iterator of the Keys in the tree.
   * @return inorder iterator of the Keys
   */
  public Iterator<String> keys(){
    LinkedList<String> keys = new LinkedList<String>();
    Iterator<Object> it = tree.inOrderIterator();
    while(it.hasNext()){
      Element e = (Element)it.next();
      keys.add(e.getKey());
    }
    return keys.iterator();
  }

  public String toString(){
    String result = "";
    Iterator<Object> it = tree.inOrderIterator();
    while(it.hasNext()){
      Element e = (Element)it.next();
      result += e+"\n";
    }
    return result;
  }
}