SortedMap in Java

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

Introduction to sorted Map

Keypoint:

  • SortedMap interface extends Map.
  • entries are maintained in an ascending key order.

Methods of sorted Map :

Comparator comparator( ).
Object firstKey( ).
SortedMap headMap(Object end).
Object lastKey( ).
SortedMap subMap(Object start, Object end).
SortedMap tailMap(Object start).

Example:

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"));
  }

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