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Java TreeMap floorKey() Method with Example

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

TreeMap Class floorKey() method

• floorKey() method is available in java.util package.
• floorKey() method is used to return the largest key element smaller than or equal to the given key element (key_ele) when it exists otherwise it returns null when no such key element exists.
• floorKey() 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.
• floorKey() method may throw an exception at the time of returning key elements 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 floorKey(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 largest key element (key_ele) less than or equal to the given key element otherwise it returns null when no such key element exists.

Example:

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

import java.util.*;

public class FloorKeyOfTreeMap {
    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 floorKey(4) method is used
        // to return the largest key element
        // less than or equal to the given key element
        // i.e. 4


        // Display Returned Key Element
        System.out.println("tm.floorKey(4): " + tm.floorKey(4));
    }
}

Output

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