Get the key/value of the first TreeMap element in Java

The code below shows how to retrieve the first key in a TreeMap in Java. To get the first element, you need to call the method. firstKey(), and then you can get the corresponding value.

import java.util.Iterator; 
import java.util.Map.Entry; 
import java.util.Set; 
import java.util.TreeMap; 
import java.util.Map; 
 
public class TreeMapFirstkey {
 
 public static void main(String a[]){
 // Create a TreeMap
 TreeMap< String, Integer> tmap = new TreeMap< String, Integer> (); 
 
 // Add key-value pairs to TreeMap
 tmap.put("Key1",5); 
 tmap.put("Key2",7); 
 tmap.put("Key3",2); 
 tmap.put("Key4",4); 
 
 // Get all inputs
 Set set = tmap.entrySet(); 

 // Get iterator to browse the list
 Iterator itr = set.iterator(); 
 
 // Show key-value pairs
 while(itr.hasNext()) {
 Map.Entry mentry = (Map.Entry)itr.next(); 
 System.out.print("key: "+mentry.getKey() + " - "); 
 System.out.println("Value: "+mentry.getValue()); 
 } 
 
 Entry< String,Integer> ent = tmap.firstEntry(); 
 System.out.println("First key/value element: "); 
 System.out.println(ent.getKey()+" ==> "+ent.getValue()); 
 }
}

Executing this code gives:

key: Key1 - Value: 5
key: Key2 - Value: 7
key: Key3 - Value: 2
key: Key4 - Value: 4
First key/value:  
Key1 ==> 5

References:
The firstKey()