Java: Remove and get a key-value mapping associated with the least key in a map

Last update on March 12 2025 13:32:14 (UTC/GMT +8 hours)

Write a Java program to remove and get a key-value mapping associated with the least key in a map.

Sample Solution:-

Java Code:

import java.util.*;
import java.util.Map.Entry;  
public class Example19 {  
         public static void main(String args[]) {

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

  // Put elements to the map 
  tree_map.put(10, "Red");
  tree_map.put(20, "Green");
  tree_map.put(40, "Black");
  tree_map.put(50, "White");
  tree_map.put(60, "Pink");

  // polling first entry
  System.out.println("Value before poll: " + tree_map);
  System.out.println("Value returned: " + tree_map.pollFirstEntry());
  System.out.println("Value after poll: " + tree_map);
 }
}

Sample Output:

Value before poll: {10=Red, 20=Green, 40=Black, 50=White, 60=Pink}     
Value returned: 10=Red                                                 
Value after poll: {20=Green, 40=Black, 50=White, 60=Pink}

For more Practice: Solve these Related Problems:

• Write a Java program to use pollFirstEntry() on a TreeMap to remove and return the mapping with the least key, then print the updated map.
• Write a Java program to repeatedly remove the first entry of a TreeMap using pollFirstEntry() until the map is empty.
• Write a Java program to implement a method that removes the first entry of a TreeMap and prints both the removed entry and the new first key.
• Write a Java program to compare the size of a TreeMap before and after removing the least key using pollFirstEntry().

Java Code Editor:

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