﻿ Java: Find the least key greater than or equal to the key

# Java Collection, TreeMap Exercises: Get a key-value mapping associated with the least key greater than or equal to the given key

## Java Collection, TreeMap Exercises: Exercise-25 with Solution

Write a Java program to get a key-value mapping associated with the least key greater than or equal to the given key. Return null if there is no such key.

Sample Solution:-

Java Code:

``````import java.util.*;
import java.util.Map.Entry;
public class Example25 {
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(30, "Black");
tree_map.put(40, "White");
tree_map.put(50, "Pink");
System.out.println("Orginal TreeMap content: " + tree_map);
System.out.println("Keys greater than or equal to 20: " + tree_map.ceilingEntry(20));
System.out.println("Keys greater than or equal to 40: " + tree_map.ceilingEntry(40));
System.out.println("Keys greater than or equal to 50: " + tree_map.ceilingEntry(50));
}
}
``````

Sample Output:

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

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