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Java TreeMap higherKey() Method with Example

TreeMap Class higherKey() method: Here, we are going to learn about the higherKey() method of TreeMap Class with its syntax and example.
Submitted by Preeti Jain, on February 29, 2020

TreeMap Class higherKey() method

• higherKey() method is available in java.util package.
• higherKey() method is used to return the lowest key value element higher than the given key element (key_ele).
• higherKey() method is a non-static method, it is accessible with the class object only and if we try to access the method with the class name then we will get an error.
• higherKey() method may throw an exception at the time of returning an appropriate key element from this map.
  • ClassCastException: This exception may throw when the given parameter is incompatible to compare with.
  • NullPointerException: This exception may throw when the given element is null exists.

Syntax:

    public Key higherKey(Key key_ele);

Parameter(s):

• Key key_ele – represents the key element to compare with.

Return value:

The return type of the method is Key, it retrieves the lowest value key element that is higher than the given key element (key_ele) otherwise it returns null.

Example:

// Java program to demonstrate the example 
// of Key higherKey(Key key_ele) 
// method of TreeMap 

import java.util.*;

public class HigherKeyOfTreeMap {
    public static void main(String[] args) {

        // Instantiates TreeMap
        TreeMap < Integer, String > tm = new TreeMap < Integer, String > ();

        // By using put() method is
        // to put the key-value pairs in
        // treemap tm
        tm.put(1, "C");
        tm.put(4, "C++");
        tm.put(3, "Java");
        tm.put(2, "Php");

        // Display TreeMap tm
        System.out.println("tm: " + tm);

        // By using higherKey(3) method is
        // return the lowest key element 
        // higher than the given key element i.e. 4
        // Display Returned Key Element
        System.out.println("tm.higherKey(): " + tm.higherKey(3));
    }
}

Output

tm: {1=C, 2=Php, 3=Java, 4=C++}
tm.higherKey(): 4