Java: Get the least key greater than or equal to the given key

Last update on May 23 2025 13:08:39 (UTC/GMT +8 hours)

26. Get Ceiling Key in TreeMap

Write a Java program to get the least key greater than or equal to the given key. Returns null if there is no such key.

Sample Solution:-

Java Code:

import java.util.*;
import java.util.Map.Entry;  
public class Example26 {  
          public static void main(String args[]) {
  // Declare tree maps
  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");
  System.out.println("Orginal TreeMap content: " + tree_map);
  System.out.println("Keys greater than or equal to 20: " + tree_map.ceilingKey(20));
  System.out.println("Keys greater than or equal to 30: " + tree_map.ceilingKey(30));
  System.out.println("Keys greater than or equal to 50: " + tree_map.ceilingKey(50));
 }
}

Sample Output:

Orginal TreeMap content: {10=Red, 20=Green, 40=Black, 50=White, 60=Pink
}                                                                      
Keys greater than or equal to 20: 20                                   
Keys greater than or equal to 30: 40                                   
Keys greater than or equal to 50: 50

For more Practice: Solve these Related Problems:

Write a Java program to use ceilingKey() on a TreeMap to get the least key that is greater than or equal to a specified value.
Write a Java program to implement a method that retrieves the ceiling key and returns a default value if no key exists.
Write a Java program to compare the result of ceilingKey() with a custom search algorithm using Java streams.
Write a Java program to iterate over the TreeMap’s key set and manually determine the ceiling key, then compare it with ceilingKey()’s result.

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