java.util.TreeMap.firstEntry() Method

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Description

The firstEntry() method is used to return a key-value mapping associated with the least key in this map, or null if the map is empty.

Declaration

Following is the declaration for java.util.TreeMap.firstEntry() method.

public Map.Entry<K,V> firstEntry()

Parameters

  • NA

Return Value

The method call returns an entry with the least key, or null if this map is empty.

Exception

  • NA

Example

The following example shows the usage of java.util.TreeMap.firstEntry() method.

package com.tutorialspoint;

import java.util.*;

public class TreeMapDemo {
   public static void main(String[] args) {
      // creating tree map 
      TreeMap<Integer, String> treemap = new TreeMap<Integer, String>();
      
      // populating tree map
      treemap.put(2, "two");
      treemap.put(1, "one");
      treemap.put(3, "three");
      treemap.put(6, "six");
      treemap.put(5, "five");
      
      System.out.println("Checking first entry");
      System.out.println("First entry is: "+ treemap.firstEntry());
   }    
}

Let us compile and run the above program, this will produce the following result.

Checking first entry
First entry is: 1=one



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