What is the TreeMap.firstEntry() method in Java?
Introduction
The TreeMap.firstEntry() method is used to obtain the key-value mapping associated with the lowest key in the map.
The TreeMap.firstEntry() method is present in the TreeMap class inside the java.util package.
Syntax
The syntax of the TreeMap.firstEntry() method is given below:
Map.entry firstEntry()
Parameters TreeMap.firstEntry() does not accept any parameters.
Return value
The TreeMap.firstEntry() method returns one value:
Entry: The key-value pair associated with the lowest key in the map.
Code
Let’s have a look at the code.
import java.util.*;class Main{public static void main(String[] args){TreeMap<Integer, String> t1 = new TreeMap<Integer, String>();t1.put(1, "Let's");t1.put(5, "see");t1.put(2, "TreeMap class");t1.put(27, "methods");t1.put(9, "in java.");System.out.println("The key-value mapping associated with " +"the lowest key in the map is: " + t1.firstEntry());TreeMap<String, Integer> t2 = new TreeMap<String, Integer>();t2.put("ab", 5);t2.put("baa", 1);t2.put("cbc", 2);t2.put("d", 27);t2.put("e", 9);System.out.println("The key-value mapping associated with " +"the lowest key in the map is: " + t2.firstEntry());}}
Explanation
-
In line 1, we import the required package.
-
In line 2, we make a
Mainclass. -
In line 4, we make a
main()function. -
In line 6, we declare a
TreeMapthat consists of keys of typeIntegerand values of typeString. -
In lines 8 to 12, we use the
TreeMap.put()method to insert values in theTreeMap. -
In line 14, we use the
TreeMap.firstEntry()method and display the key-value pair associated with the lowest key in the map with a message. -
In lines 17 to 26, we create another
TreeMapobject that contains keys of typeStringand values of typeInteger. Then, we can see from the output that the lowest key in the case of strings would be considered based on alphabetic order.
So, this is the way to use the TreeMap.firstEntry() method in Java.
