TreeMap firstEntry() and firstKey() Method in Java with Examples
There are two variants of first() in Java.util.TreeMap, both are discussed in this article.
Method 1: firstEntry()
It returns a key-value mapping associated with the least key in this map, or null if the map is empty.
Syntax:
public Map.Entry firstEntry()
Return Type: An entry with the least key and null if the map is empty.
Example:
Output:
Lowest entry is: 1=one
Method 2: firstKey()
It returns the first (lowest) key currently in the map.
Syntax:
public K firstKey()
Return Type: The first (lowest) key currently in this map.
Exception Thrown: NoSuchElementException is thrown if this map is empty.
Example:
Java
import java.io.*;
import java.util.*;
class GFG {
public static void main(String[] args)
{
TreeMap<Integer, String> treemap
= new TreeMap<Integer, String>();
treemap.put( 2 , "two" );
treemap.put( 1 , "one" );
treemap.put( 3 , "three" );
treemap.put( 6 , "six" );
treemap.put( 5 , "five" );
treemap.put( 9 , "nine" );
System.out.println( "Lowest key is: "
+ treemap.firstKey());
}
}
|
Output:
Lowest key is: 1
Implementation: These functions can be used to fetch the best-ranked person in the given list, or can be used to assign a winner in which person with the lowest time to finish a task wins. The latter one is discussed below.
Example: Practical Application
Java
import java.io.*;
import java.util.*;
public class GFG {
public static void main(String[] args)
{
TreeMap<Float, String> time
= new TreeMap<Float, String>();
time.put( 2 .32f, "Astha" );
time.put( 7 .43f, "Manjeet" );
time.put( 1 .3f, "Shambhavi" );
time.put( 5 .63f, "Nikhil" );
time.put( 6 .26f, "Vaishnavi" );
System.out.println( "Winner with lowest time is : "
+ time.firstEntry());
}
}
|
Output:
Winner with lowest time is : 1.3=Shambhavi
Last Updated :
20 Nov, 2021
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