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Categories / Java Tutorial / Collections

 

Working with End Points

The firstKey() and lastKey() methods of TreeMap let you quickly access the keys at the end of the map. If you need to traverse a map backwards(keep getting the last key and the head map before it): import java.util.TreeMap; public class MainClass {   public static void main(String[] a) {     TreeMap map = new TreeMap();     map.put("key1", "value1");     map.put("key2", "value2");     map.put("key3", "value3");     if (!map.isEmpty()) {       Object last = map.lastKey();       boolean first = true;       do {         if (!first) {           System.out.print(", ");         }         System.out.print(last);         last = map.headMap(last).lastKey();         first = false;       } while (last != map.firstKey());       System.out.println();     }   } } key3, key2