Check out example codes for "TreeMap lowerKey(K key) method in java". It will help you in understanding the concepts better.

Code Example 1

import java.util.TreeMap;
public class TreeMapLowerKeyMethodExample
{
   public static void main(String[] args)
   {
      TreeMap<Integer, String> tm = new TreeMap<Integer, String>();
      tm.put(8, "mango");
      tm.put(5, "apple");
      tm.put(3, "watermelon");
      tm.put(7, "pineapple");
      tm.put(6, "orange");
      tm.put(9, "grapes");
      System.out.println("TreeMap: " + tm.toString());
      // here 10 is not available it returns 9
      System.out.print("Lower Key Entry of Element 10 is: ");
      System.out.println(tm.lowerKey(10));
      System.out.print("Lower Key Entry of Element 5 is: ");
      System.out.println(tm.lowerKey(5));
   }
}

Code Example 2

example on TreeMap lowerKey(K key) method for NullPointerException
import java.util.TreeMap;
public class TreeMapLowerKeyMethodExample
{
   public static void main(String[] args)
   {
      TreeMap<Integer, String> tm = new TreeMap<Integer, String>();
      tm.put(8, "mango");
      tm.put(5, "apple");
      tm.put(3, "watermelon");
      tm.put(7, "pineapple");
      tm.put(6, "orange");
      tm.put(9, "grapes");
      System.out.println("TreeMap: " + tm.toString());
      try
      {
         // pass null as parameter to lowerKey() method
         System.out.println(tm.lowerKey(null));
      }
      catch(Exception ex)
      {
         System.out.println("Exception: " + ex);
      }
   }
}

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