The lowerEntry() method of java.util.TreeMap class is used to return a key-value mapping associated with the greatest key strictly less than the given key, or null if there is no such key
Syntax:
public Map.Entry lowerEntry(K key)
Parameters: This method takes the key as a parameter for which the lower entry is to be found.
Return Value: This method returns an entry with the greatest key less than key, or null if there is no such key.
Exception: This method throws NullPointerException if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys.
Below are the examples to illustrate the lowerEntry() method
Example 1:
// Java program to demonstrate // lowerEntry() method // for <Integer, String> import java.util.*;
public class GFG1 {
public static void main(String[] argv)
throws Exception
{
try {
// creating object of TreeMap<Integer, String>
TreeMap<Integer, String>
treemap = new TreeMap<Integer, String>();
// populating tree map
treemap.put( 1 , "One" );
treemap.put( 2 , "Two" );
treemap.put( 3 , "Three" );
treemap.put( 4 , "Four" );
treemap.put( 5 , "Five" );
// printing the TreeMap
System.out.println( "TreeMap: " + treemap);
// getting lowerEntry value for 3
// using lowerEntry() method
Map.Entry<Integer, String>
value
= treemap.lowerEntry( 3 );
// printing the value
System.out.println( "The lowerEntry value "
+ " for 3: " + value);
}
catch (NullPointerException e) {
System.out.println( "Exception thrown : " + e);
}
}
} |
TreeMap: {1=One, 2=Two, 3=Three, 4=Four, 5=Five} The lowerEntry value for 3: 2=Two
Example 2: For NullPointerException
// Java program to demonstrate // lowerEntry() method // for NullPointerException import java.util.*;
public class GFG1 {
public static void main(String[] argv)
throws Exception
{
try {
// creating object of TreeMap<Integer, String>
TreeMap<Integer, String>
treemap = new TreeMap<Integer, String>();
// populating tree map
treemap.put( 1 , "One" );
treemap.put( 2 , "Two" );
treemap.put( 3 , "Three" );
treemap.put( 4 , "Four" );
treemap.put( 5 , "Five" );
// printing the TreeMap
System.out.println( "TreeMap: " + treemap);
// getting lowerEntry value for null
// using lowerEntry() method
System.out.println( "Trying to get"
+ " the lowerEntry value"
+ " for value NULL" );
Map.Entry<Integer, String>
value
= treemap.lowerEntry( null );
// printing the value
System.out.println( "Value is: " + value);
}
catch (NullPointerException e) {
System.out.println( "Exception thrown : " + e);
}
}
} |
TreeMap: {1=One, 2=Two, 3=Three, 4=Four, 5=Five} Trying to get the lowerEntry value for value NULL Exception thrown : java.lang.NullPointerException