Create a TreeMap in Java and add key-value pairs

A TreeMap cannot contain duplicate keys. TreeMap cannot contain the null key. However, It can have null values.

Let us first see how to create a TreeMap −

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

Add some elements in the form of key-value pairs −

m.put(1,"India");
m.put(2,"US");
m.put(3,"Australia");
m.put(4,"Netherlands");
m.put(5,"Canada");

The following is an example to create a TreeMap and add key-value pairs −

Example

 Live Demo

import java.util.*;
public class Demo {
   public static void main(String args[]) {
      TreeMap<Integer,String> m = new TreeMap<Integer,String>();
      m.put(1,"India");
      m.put(2,"US");
      m.put(3,"Australia");
      m.put(4,"Netherlands");
      m.put(5,"Canada");
      for(Map.Entry e:m.entrySet()) {
         System.out.println(e.getKey()+" "+e.getValue());
      }
   }
}

Output

1 India
2 US
3 Australia
4 Netherlands
5 Canada