Java - The SortedMap Interface

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The SortedMap interface extends Map. It ensures that the entries are maintained in ascending key order

Several methods throw a NoSuchElementException when no items are in the invoking map. A ClassCastException is thrown when an object is incompatible with the elements in a map. A NullPointerException is thrown if an attempt is made to use a null object when null is not allowed in the map.

The methods declared by SortedMap are summarized in the following table:

SN	Methods with Description
1	Comparator comparator( ) Returns the invoking sorted map‘s comparator. If the natural ordering is used for the invoking map, null is returned.
2	Object firstKey( ) Returns the first key in the invoking map.
3	SortedMap headMap(Object end) Returns a sorted map for those map entries with keys that are less than end.
4	Object lastKey( ) Returns the last key in the invoking map.
5	SortedMap subMap(Object start, Object end) Returns a map containing those entries with keys that are greater than or equal to start and less than end
6	SortedMap tailMap(Object start) Returns a map containing those entries with keys that are greater than or equal to start.

Example:

SortedMap have its implementation in various classes like TreeMap, Following is the example to explain SortedMap functionlaity:

import java.util.*;public class TreeMapDemo {   public static void main(String args[]) {      // Create a hash map      TreeMap tm = new TreeMap();      // Put elements to the map      tm.put("Zara", new Double(3434.34));      tm.put("Mahnaz", new Double(123.22));      tm.put("Ayan", new Double(1378.00));      tm.put("Daisy", new Double(99.22));      tm.put("Qadir", new Double(-19.08));        // Get a set of the entries      Set set = tm.entrySet();      // Get an iterator      Iterator i = set.iterator();      // Display elements      while(i.hasNext()) {         Map.Entry me = (Map.Entry)i.next();         System.out.print(me.getKey() + ": ");         System.out.println(me.getValue());      }      System.out.println();      // Deposit 1000 into Zara‘s account      double balance = ((Double)tm.get("Zara")).doubleValue();      tm.put("Zara", new Double(balance + 1000));      System.out.println("Zara‘s new balance: " +      tm.get("Zara"));   }}

This would produce the following result:

Ayan: 1378.0Daisy 99.22Mahnaz: 123.22Qadir: -19.08Zara: 3434.34Zara.s current balance: 4434.34

Java - The SortedMap Interface