Java : Collection Framework : TreeMap (decendingKeySet)

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TreeMapExample.java

import java.util.NavigableSet;
import java.util.TreeMap;

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

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

        treeMap.put(10, "Cat");
        treeMap.put(40, "Dog");
        treeMap.put(30, "Apple");
        treeMap.put(20, "Ball");
        

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

        /*
         * Returns a reverse order NavigableSet view of the keys contained in
         * this map. The set's iterator returns the keys in descending order.
         * 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.
         */
        NavigableSet<Integer> navigableSet = treeMap.descendingKeySet();

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

        for( Integer key : navigableSet )
        {
            System.out.println(key);
        }

    }
}

Output

treeMap : {10=Cat, 20=Ball, 30=Apple, 40=Dog}

navigableSet : [40, 30, 20, 10]

40
30
20
10

To Download TreeMapDemoDescendingKeySet Project Click the below link
https://sites.google.com/site/javaee4321/java-collections/TreeMapDemoDescendingKeySet.zip?attredirects=0&d=1

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