Java: Get the first (lowest) key and the last (highest) key currently in a map

Last update on March 12 2025 13:34:06 (UTC/GMT +8 hours)

Write a Java program to get the first (lowest) key and the last (highest) key currently in a map.

Sample Solution:-

Java Code:

import java.util.*;
import java.util.Map.Entry;  
public class Example9 {  
     public static void main(String args[]) {

  // Create a tree map
  TreeMap <String,String> tree_map1 = new TreeMap <String,String> ();

  // Put elements to the map 
  tree_map1.put("C2", "Red");
  tree_map1.put("C1", "Green");
  tree_map1.put("C4", "Black");
  tree_map1.put("C3", "White");

  System.out.println("Orginal TreeMap content: " + tree_map1);
  System.out.println("Greatest key: " + tree_map1.firstKey());
  System.out.println("Least key: " + tree_map1.lastKey());
 }
}

Sample Output:

Orginal TreeMap content: {C1=Green, C2=Red, C3=White, C4=Black}        
Greatest key: C1                                                       
Least key: C4

For more Practice: Solve these Related Problems:

• Write a Java program to retrieve the first key using firstKey() and the last key using lastKey() of a TreeMap and print them.
• Write a Java program to verify that the first key is the minimum and the last key is the maximum by comparing with a sorted list.
• Write a Java program to remove the first key using pollFirst() and then print the new first key of the TreeMap.
• Write a Java program to compare the results of firstKey() and lastKey() from two TreeMaps and output the difference.

Java Code Editor:

Contribute your code and comments through Disqus.

Previous: Get a key-value mapping associated with the greatest key and the least key in a map.
Next: Get a reverse order view of the keys contained in a given map.