TreeMap ceilingKey() method in Java

We will learn about treemap ceilingKey () method in java in this tutorial .  Java TreeMap ceilingKey() method returns the least key greater than or equal to the given key, or null if there is no such key.

Syntax :

public K ceilingKey(K key)

Parameters : This is the given key to be matched.

Return Value : It’s return the least key greater than or equal to key, or null if there is no such key .

Exception : Java ThreeMap ceilingkey () method throws following exceptions .

ClassCastException – if the given key cannot be compared with the keys in the map
NullPointerException – if the given key is null and this map uses natural ordering, or its comparator does not permit null keys.

Now we will discuss different examples of  ceilingKey() method .

Example 1 : Java TreeMap ceilingKey() method – Return least greater than or equal Key

In this example we create TreeMap and add element in it . Now we use ceilingKey() method with 9,7,2 and 1 key . Because here maximum value of key is 9 , So for ceilingKey(10) it returns 9 . for ceilingKey(7) it returns 9 because 9 is least greater than key in TreeMap for key 7. for ceilingKey(2) , its return 2 and floorKey(1) , it’s return 2 .

import java.util.TreeMap;

public class JavaTreeMapceilingKey {
	
	public static void main(String[] args) {
		
		TreeMap<Integer,String> treeMap = new TreeMap<Integer,String>();


    	treeMap.put(2, "vogue");
    	treeMap.put(3,"welcomes");
    	treeMap.put(4,"you");
    	treeMap.put(6,"java");
    	treeMap.put(5,"map");
    	treeMap.put(9,"php");
    	
        //print TreeMap Elements 
    	System.out.println("TreeMap Elements : "+ treeMap);

    	//print ceilingKey For key 9
    	System.out.println("treeMap.ceilingKey(9) : "+ treeMap.ceilingKey(9));
    	
    	//print ceilingKey For key 7
    	System.out.println("treeMap.ceilingKey(7) : "+ treeMap.ceilingKey(7));
    	
    	//print ceilingKey For key 2
    	System.out.println("treeMap.ceilingKey(2) : "+ treeMap.ceilingKey(2));
    	
    	//print ceilingKey For key 1
    	System.out.println("treeMap.ceilingKey(1) : "+ treeMap.ceilingKey(1));

		
	}

}

Output:

TreeMap Elements : {2=vogue, 3=welcomes, 4=you, 5=map, 6=java, 9=php}
treeMap.ceilingKey(9) : 9
treeMap.ceilingKey(7) : 9
treeMap.ceilingKey(2) : 2
treeMap.ceilingKey(1) : 2

Example 2: Java TreeMap ceilingKey() method – Return null key

TreeMap ceilingKey() method will return null key if there is no least greater than or equal to key of given key.  Greater key value is 9 in this example for TreeMap . So treeMap.ceilingKey(10) and treeMap.ceilingKey(11) will return null in this example.

import java.util.TreeMap;

public class JavaTreeMapceilingKey1 {

	public static void main(String[] args) {
		
		TreeMap<Integer,String> treeMap = new TreeMap<Integer,String>();

    	treeMap.put(1,"java");
    	treeMap.put(2, "vogue");
    	treeMap.put(3,"welcomes");
    	treeMap.put(4,"you");
    	treeMap.put(5,"map");
    	treeMap.put(9,"php");
    	
        //print TreeMap Elements 
    	System.out.println("TreeMap Elements : "+ treeMap);

    	//print ceilingKey For key 10
    	System.out.println("treeMap.ceilingKey(10) : "+ treeMap.ceilingKey(10));
    	
    	//print ceilingKey For key 11
    	System.out.println("treeMap.ceilingKey(11) : "+ treeMap.ceilingKey(11));
    	
    	//print ceilingKey For key 30
    	System.out.println("treeMap.ceilingKey(30) : "+ treeMap.ceilingKey(30));

	}
}

Output :

TreeMap Elements : {1=java, 2=vogue, 3=welcomes, 4=you, 5=map, 9=php}
treeMap.ceilingKey(10) : null
treeMap.ceilingKey(11) : null
treeMap.ceilingKey(30) : null

Exaample 3 : Java TreeMap ceilingKey() method – NullPointerException

We will use null key then TreeMap ceilingKey() method will throw null pointer exception

import java.util.TreeMap;

public class JavaTreeMapceilingKey2 {
	
	public static void main(String[] args) {
		
		TreeMap<Integer,String> treeMap = new TreeMap<Integer,String>();

    	treeMap.put(1,"java");
    	treeMap.put(2, "vogue");
    	treeMap.put(3,"welcomes");
    	treeMap.put(4,"you");
    	treeMap.put(5,"map");
    	treeMap.put(9,"php");
    	
        //print TreeMap Elements 
    	System.out.println("TreeMap Elements : "+ treeMap);
    	
    	
    	try{
    		
        	System.out.println(" "+ treeMap.ceilingKey(null));
        	
        	}catch(Exception e){
        		System.out.println("Exception : "+ e);
        	}
		
	}

}

Output :

TreeMap Elements : {1=java, 2=vogue, 3=welcomes, 4=you, 5=map, 9=php}
Exception : java.lang.NullPointerException

Example 4 : Java TreeMap ceilingKey() method – ClassCastException

Java TreeMap ceilingKey() method throws ClassCastException if the given key cannot be compared with the keys in the map . Let’s see java treemap ceilingkey example for ClassCastException .

import java.util.TreeMap;

public class JavaTreeMapceilingKey3 {
	
	
	public static void main(String[] args) {
		
		TreeMap<Object,String> treeMap = new TreeMap<Object,String>();

    	treeMap.put(1,"java");
    	treeMap.put(2, "vogue");
    	treeMap.put(3,"welcomes");
    	treeMap.put(4,"you");
    	treeMap.put(5,"map");
    	treeMap.put(9,"php");
    	
        //print TreeMap Elements 
    	System.out.println("TreeMap Elements : "+ treeMap);
    	
    	try{
    		
        	System.out.println(" "+ treeMap.ceilingKey(new String("JavaMap") ));
        	
        	}catch(Exception e){
        		System.out.println("Exception : "+ e);
        	}
	
	}

}

Output:

TreeMap Elements : {1=java, 2=vogue, 3=welcomes, 4=you, 5=map, 9=php}
Exception : java.lang.ClassCastException: java.lang.Integer cannot
 be cast to java.lang.String

In this tutorial we have learned java treemap ceilingKey() method . you can see more good java TreeMap Examples for practice .

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