Java Collection Tutorial - Java TreeMap.firstKey()

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Syntax

TreeMap.firstKey() has the following syntax.

public K firstKey()

Example

In the following code shows how to use TreeMap.firstKey() method.

import java.util.TreeMap;
//from w w  w  .  j  av  a2  s  .co m
public class Main {
   public static void main(String[] args) {
      
      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, "from java2s.com");
      
      System.out.println("Checking first key");
      System.out.println("First key is: "+ treemap.firstKey());
   }    
}

The code above generates the following result.

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