TreeMap floorKey() in Java with Examples
Last Updated :
17 Sep, 2018
Pre-requisite: TreeMap in Java
The floorKey() method is used to return the greatest key less than or equal to given key from the parameter.
Syntax:
public K floorKey(K key)
Parameter: This method accepts a mandatory parameter key which is the key to be matched.
Return Value: The method call returns the greatest key less than or equal to key, or null if there is no such key.
Exception: This method throws following exceptions:
- ClassCastException: When the specified key cannot be compared with the key available in Map.
- NullPointerException: When the specified key in map is null and it uses natural
ordering which means, comparator does not permit null keys.
Below are examples to illustrate the use of floorKey() method:
Example 1:
import java.util.TreeMap;
public class FloorKeyDemo {
public static void main(String args[])
{
TreeMap<Integer, String> numMap = new TreeMap<Integer, String>();
numMap.put( 6 , "Six" );
numMap.put( 1 , "One" );
numMap.put( 5 , "Five" );
numMap.put( 3 , "Three" );
numMap.put( 8 , "Eight" );
numMap.put( 10 , "Ten" );
System.out.println( "TreeMap: " + numMap.toString());
System.out.print( "Floor Entry of Element 11 is: " );
System.out.println(numMap.floorKey( 11 ));
System.out.print( "Floor Entry of Element 0 is: " );
System.out.println(numMap.floorKey( 0 ));
}
}
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Output:
TreeMap: {1=One, 3=Three, 5=Five, 6=Six, 8=Eight, 10=Ten}
Floor Entry of Element 11 is: 10
Floor Entry of Element 0 is: null
Example 2: To demonstrate NullPointerException
import java.util.TreeMap;
public class FloorKeyDemo {
public static void main(String args[])
{
TreeMap<Integer, String>
numMap = new TreeMap<Integer, String>();
numMap.put( 6 , "Six" );
numMap.put( 1 , "One" );
numMap.put( 5 , "Five" );
numMap.put( 3 , "Three" );
numMap.put( 8 , "Eight" );
numMap.put( 10 , "Ten" );
System.out.println( "TreeMap: " + numMap.toString());
try {
System.out.println(numMap.floorKey( null ));
}
catch (Exception e) {
System.out.println( "Exception: " + e);
}
}
}
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Output:
TreeMap: {1=One, 3=Three, 5=Five, 6=Six, 8=Eight, 10=Ten}
Exception: java.lang.NullPointerException
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