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The lowerEntry() method of NavigableMap interface in Java is used to return a key-value mapping associated with the greatest key strictly less than the given key, or null if there is no such key existed. Syntax:

Map.Entry< K, V > lowerEntry(K key)

Where, K is the type of key maintained by this map and V is the type of values mapped to the keys. Parameters: This function accepts a single parameter Key which refers to the type of key maintained by this map container. Return Value: It returns a key-value mapping associated with the greatest key strictly less than the given key, or null if there is no such key existed. Below programs illustrate the lowerEntry() method in Java: Program 1: When the key is integer.

Java

// Java code to demonstrate the working of
// lowerEntry() method

import java.io.*;
import java.util.*;

public class GFG {

    public static void main(String[] args)
    {

        // Declaring the NavigableMap of Integer and String
        NavigableMap<Integer, String> nmmp = new TreeMap<>();

        // assigning the values in the NavigableMap
        // using put()
        nmmp.put(2, "two");
        nmmp.put(7, "seven");
        nmmp.put(3, "three");

        System.out.println("The mapping with greatest key strictly"
                           + " less than 7 is : " + nmmp.lowerEntry(7));
    }
}

Output:

The mapping with greatest key strictly less than 7 is : 3=three

Program 2: When the key is string.

Java

// Java code to demonstrate the working of
// lowerEntry() method

import java.io.*;
import java.util.*;

public class GFG {

    public static void main(String[] args)
    {

        // Declaring the NavigableMap of Integer and String
        NavigableMap<String, String> tmmp = new TreeMap<>();

        // assigning the values in the NavigableMap
        // using put()
        tmmp.put("one", "two");
        tmmp.put("six", "seven");
        tmmp.put("two", "three");

        System.out.println("The mapping with greatest key strictly"
                           + " less than 7 is : " + tmmp.lowerEntry("two"));
    }
}

Output:

The mapping with greatest key strictly less than 7 is : six=seven

Reference: https://docs.oracle.com/javase/10/docs/api/java/util/NavigableMap.html#lowerEntry(K)

NavigableMap lowerEntry() method in Java

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