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Sorted Map - Java Example Program


Sorted Map
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import java.util.TreeMap;

class SortedMapTest
{
    public static void main(String arg[])
    {
        TreeMap<String, Double> tm = new TreeMap<String, Double>();
        tm.put("Santosh", new Double(3020.55));
        tm.put("Ram", new Double(2550.22));
        tm.put("Nishan", new Double(2060.66));
        tm.put("Amar", new Double(1890.88));
        tm.put("Om", new Double(1650.11));
        System.out.println("Map after initialization : " + tm);
        
        Set set = tm.entrySet(); // Setting entry set
        Iterator i = set.iterator(); // Iterating to set
        while (i.hasNext()) {
            // Assigning iterator to map entry
            Map.Entry m = (Map.Entry) i.next();
            if (m.getKey().equals("Ram")) {
                m.setValue(3550.33); // Set value for Ram key
            }
            // Getting key and value from map entry
            System.out.println(m.getKey() + " : " + m.getValue());
        }
        System.out.println("Map after changing Ram value : " + tm);
        
        System.out.println("First key : " + tm.firstKey());
        System.out.println("Last key : " + tm.lastKey());
        System.out.println("Keys set : " + tm.keySet());
        System.out.println("Values set : " + tm.values());
        System.out.println("Head map : " + tm.headMap("Om"));
        System.out.println("Sub map : " + tm.subMap("Nishan", "Santosh"));
        System.out.println("Tail map : " + tm.tailMap("Om"));
    
    }
}
OUTPUT

Map after initialization : {Amar=1890.88, Nishan=2060.66, Om=1650.11, Ram=2550.22, Santosh=3020.55}
Amar : 1890.88
Nishan : 2060.66
Om : 1650.11
Ram : 3550.33
Santosh : 3020.55
Map after changing Ram value : {Amar=1890.88, Nishan=2060.66, Om=1650.11, Ram=3550.33, Santosh=3020.55}
First key : Amar
Last key : Santosh
Keys set : [Amar, Nishan, Om, Ram, Santosh]
Values set : [1890.88, 2060.66, 1650.11, 3550.33, 3020.55]
Head map : {Amar=1890.88, Nishan=2060.66}
Sub map : {Nishan=2060.66, Om=1650.11, Ram=3550.33}
Tail map : {Om=1650.11, Ram=3550.33, Santosh=3020.55}

DESCRIPTION

In this program, a TreeMap of key type String and value type Double is taken which stores elements in a ascending order. Five elements are added to the tree map, then entry set is assigned to set, set is assigned to iterator, and the iterator elements are assigned to map entry to retrieve the keys and values. Few methods of sorted map are used to retrieve required elements.

THINGS TO TRY
  • Add Prakash and 4500.45 into tree map by using put method.
  • In equals method give Amar and set value to 1500.60.
  • Create a new tree map with key type as String i.e. subjects and value type as Integer i.e. marks, add the marks to subjects, this will store the elements in ascending order. Try calling sorted map methods.

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