Get first key from NavigableMap in Java

To display the first key from NavigableMap in Java, use the firstKey() method.

Let us first create NavigableMap −

NavigableMap<String, Integer> n = new TreeMap<String, Integer>();
n.put("A", 498);
n.put("B", 389);
n.put("C", 868);
n.put("D", 988);
n.put("E", 686);
n.put("F", 888);
n.put("G", 999);
n.put("H", 444);
n.put("I", 555);
n.put("J", 666);

Get the first key now −

n.firstKey()

The following is an example to get the first key from NavigableMap −

Example

 Live Demo

import java.util.*;
public class Demo {
   public static void main(String[] args) {
      NavigableMap<String, Integer> n = new TreeMap<String, Integer>();
      n.put("A", 498);
      n.put("B", 389);
      n.put("C", 868);
      n.put("D", 988);
      n.put("E", 686);
      n.put("F", 888);
      n.put("G", 999);
      n.put("H", 444);
      n.put("I", 555);
      n.put("J", 666);
      System.out.println("NavigableMap elements...
"+n);
      System.out.println("First Key = "+n.firstKey());
   }
}

Output

NavigableMap elements...
{A=498, B=389, C=868, D=988, E=686, F=888, G=999, H=444, I=555, J=666}
First Key = A