import java.util.Set;
import java.util.TreeMap;

/*
 * Example of keySet() method.
 */
public class TreeMapExample
{
    public static void main( String[] args )
    {

        TreeMap<Integer, String> treeMap = new TreeMap<Integer, String>();

        treeMap.put(1, "Cat");
        treeMap.put(2, "Dog");
        treeMap.put(4, "Apple");
        treeMap.put(3, "Ball");

        System.out.println("treeMap : " + treeMap + "\n");

        /*
         * Returns a Set view of the keys contained in this map. The set is
         * backed by the map, so changes to the map are reflected in the set,
         * and vice-versa.
         * 
         * If the map is modified while an iteration over the set is in progress
         * (except through the iterator's own remove operation), the results of
         * the iteration are undefined. The set supports element removal, which
         * removes the corresponding mapping from the map, via the
         * Iterator.remove, Set.remove, removeAll, retainAll, and clear
         * operations. It does not support the add or addAll operations.
         */
        Set<Integer> set = treeMap.keySet();

        System.out.println("set : " + set + "\n");

        System.out.println("-----------------------");
        System.out.println("Key" + " | " + "value");
        System.out.println("-----------------------");

        for( Integer key : set )
        {
            String value = treeMap.get(key);
            System.out.println(key + "   |  " + value);

        }

    }
}