TreeMap firstEntry() refers to the method used to retrieve the key-value pairs mapped with the lowest key value element that exists in the TreeMap, if there are no key-value pairs within the Map, simply returns null. The method name ‘firstEntry()’ explains itself that it will return entry having the least key element with its value.
Syntax: public Map.Entry<K,V> firstEntry(), Here K and V refer key-value respectively. Parameters: NA - As it doesnot accept any parameter. Return Value: It returns an entry with the least key (lowest key-value pair) and null if the TreeMap is empty. Exception: NA - As it doesnot throw any exception at entry return.
Example 1:
Java
// Java code to demonstrate // the working of TreeMap firstKey() import java.io.*;
import java.util.*;
public class treeMapFirstKey {
public static void main(String[] args)
{
// Declaring the TreeMap of Key - Value Pairs
// Integer - Key , String - Value
TreeMap<Integer, String> treemap = new TreeMap<Integer, String>();
// Adding-up the values in the TreeMap
// Use put() function to append data
treemap.put( 2 , "Java" );
treemap.put( 4 , "CPP" );
treemap.put( 5 , "PHP" );
treemap.put( 1 , "Python" );
treemap.put( 3 , "C" );
// Check for firstEntry()
System.out.println( "Lowest Entry is: " + treemap.firstEntry());
}
} |
Output
Lowest Entry is: 1=Python
By the above example, it’s clear that firstEntry() checks compare each key of TreeMap, and returns having the least key-value pair.
Example 2:
Java
// Java code to demonstrate the working // of TreeMap firstKey() method import java.io.*;
import java.util.*;
public class percentageFirstKey {
public static void main(String[] args)
{
// Declaring the TreeMap of Key - Value Pairs
// Double - Key , String - Value
TreeMap<Double, String> treemapPercentage = new TreeMap<Double, String>();
// Adding-up the values in the TreeMap
// Use put() function to append data
treemapPercentage.put( 81.40 , "Shashank" );
treemapPercentage.put( 72.80 , "Anand" );
treemapPercentage.put( 65.50 , "Gulshan" );
treemapPercentage.put( 71.10 , "Abhishek" );
treemapPercentage.put( 70.20 , "Ram" );
// Check for firstEntry()
System.out.println( "Lowest Entry is: " + treemapPercentage.firstEntry());
}
} |
Output
Lowest Entry is: 65.5=Gulshan
Some points on TreeMap firstEntry():
- TreeMap firstEntry() is available in java.util package.
- It does not throw an exception at return entry time.
- TreeMap firstEntry() method is a non-static method as it is accessible by the class’s object, other than that, will get an error.