ConcurrentSkipListMap ceilingKey() method in Java with Examples

The ceilingKey() method of java.util.concurrent.ConcurrentSkipListMap is an in-built function in Java which returns the least key greater than or equal to the given key. If there is no such value then null is returned. The method throws NullPointerException when there is no key.

Syntax:

public K ceilingKey(K key)

Parameter: The function accepts a single mandatory parameter key which specifies the key.

Return Value: The function returns the least key greater than or equal to key, or null if there is no such key.

Exceptions: The method throws two types of exceptions:

  • ClassCastException: if the specified key cannot be compared with the keys currently in the map and
  • NullPointerException: if the specified key is null.

Below programs illustrate the above above method:
Program 1:

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// Java program to demonstrate
// ceilingkey method in java
  
import java.util.concurrent.ConcurrentSkipListMap;
  
class GFG {
    public static void main(String[] args)
    {
  
        // Initializing the set
        // using ConcurrentSkipListMap()
        ConcurrentSkipListMap<Integer, Integer>
            mpp = new ConcurrentSkipListMap<Integer,
                                            Integer>();
  
        // Adding elements to this set
        mpp.put(1, 1);
        mpp.put(5, 2);
        mpp.put(2, 7);
  
        // Printing the ConcurrentSkipListMap
        // Always in ascending order
  
        System.out.println("Map: "
                           + mpp);
  
        System.out.println("key greater than or equal 3: "
                           + mpp.ceilingKey(3));
  
        System.out.println("key greater than or equal 2: "
                           + mpp.ceilingKey(2));
    }
}

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Output:

Map: {1=1, 2=7, 5=2}
key greater than or equal 3: 5
key greater than or equal 2: 2

Program 2:

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// Java program to demonstrate
// ceilingkey method in java
import java.util.concurrent.ConcurrentSkipListMap;
  
class GFG {
    public static void main(String[] args)
    {
  
        // Initializing the set
        // using ConcurrentSkipListMap()
        ConcurrentSkipListMap<Integer, Integer>
            mpp = new ConcurrentSkipListMap<Integer,
                                            Integer>();
  
        // Adding elements to this set
        mpp.put(11, 1);
        mpp.put(51, 42);
        mpp.put(92, 7);
  
        // Printing the ConcurrentSkipListMap
        // Always in ascending order
  
        System.out.println("Map: "
                           + mpp);
  
        System.out.println("key greater than or equal 11: "
                           + mpp.ceilingKey(11));
  
        System.out.println("key greater than or equal 51: "
                           + mpp.ceilingKey(51));
    }
}

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Output:

Map: {11=1, 51=42, 92=7}
key greater than or equal 11: 11
key greater than or equal 51: 51

Reference: https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/ConcurrentSkipListMap.html#ceilingKey-K-



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