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Java Collection, TreeMap Exercises: Get the least key greater than or equal to the given key

Java Collection, TreeMap Exercises: Exercise-26 with Solution

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 

Java Code Editor:

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Java: Tips of the Day

getEnumMap

Converts to enum to Map where key is the name and value is Enum itself.

public static <E extends Enum<E>> Map<String, E> getEnumMap(final Class<E> enumClass) {
    return Arrays.stream(enumClass.getEnumConstants())
            .collect(Collectors.toMap(Enum::name, Function.identity()));
}

Ref: https://bit.ly/3xXcFZt