TreeMap tailMap() Method in Java
The java.util.TreeMap.tailMap(from_Key) method in Java is used to get a part or view of the map whose keys are greater than equal to the from_key in the parameter. Any changes made in one map will reflect the change in the other map.
Syntax:
Tree_Map.tailMap(from_Key)
Parameters: The method takes one parameter from_key of the Key type in the TreeMap and refers to the key which is set as the lower point greater than whose mappings are to be returned.
Return Value: The method returns the portion of the mapping whose keys are greater than the from_Key.
Exceptions: The method throws three types of exception:
- ClassCastException: This exception is thrown if the parameters mentioned in the method cannot be compared with the keys of this map.
- NullPointerException: This exception is thrown if either of the parameters is of null type and the map does not accept any null values.
- IllegalArgumentException: This exception is thrown if the mentioned parameters are out of range or the lower end is greater than the higher end.
Below programs illustrate the working of java.util.TreeMap.tailMap() method:
Program 1:
import java.util.*;
public class Tree_Map_Demo {
public static void main(String[] args)
{
TreeMap<Integer, String> tree_map = new TreeMap<Integer, String>();
tree_map.put( 10 , "Geeks" );
tree_map.put( 15 , "4" );
tree_map.put( 20 , "Geeks" );
tree_map.put( 25 , "Welcomes" );
tree_map.put( 30 , "You" );
System.out.println( "The original map is: "
+ tree_map);
System.out.println( "The tailMap is " + tree_map.tailMap( 15 ));
}
}
|
Output:
The original map is: {10=Geeks, 15=4, 20=Geeks, 25=Welcomes, 30=You}
The tailMap is {15=4, 20=Geeks, 25=Welcomes, 30=You}
Program 2:
import java.util.*;
public class Tree_Map_Demo {
public static void main(String[] args)
{
TreeMap<String, Integer> tree_map = new TreeMap<String, Integer>();
tree_map.put( "Geeks" , 10 );
tree_map.put( "4" , 15 );
tree_map.put( "Geeks" , 20 );
tree_map.put( "Welcomes" , 25 );
tree_map.put( "You" , 30 );
System.out.println( "The original map is: "
+ tree_map);
System.out.println( "The tailMap is " + tree_map.tailMap( "Geeks" ));
}
}
|
Output:
The original map is: {4=15, Geeks=20, Welcomes=25, You=30}
The tailMap is {Geeks=20, Welcomes=25, You=30}
Program 3: By default, the from_key is included in the tail_Map. If it needs to be ignored or excluded then another parameter can be passed along with the from_key and that is false.
import java.util.*;
public class Tree_Map_Demo {
public static void main(String[] args)
{
TreeMap<String, Integer> tree_map = new TreeMap<String, Integer>();
tree_map.put( "Geeks" , 10 );
tree_map.put( "4" , 15 );
tree_map.put( "Geeks" , 20 );
tree_map.put( "Welcomes" , 25 );
tree_map.put( "You" , 30 );
System.out.println( "The original map is: "
+ tree_map);
System.out.println( "The tailMap is " + tree_map.tailMap( "Geeks" , false ));
}
}
|
Output:
The original map is: {4=15, Geeks=20, Welcomes=25, You=30}
The tailMap is {Welcomes=25, You=30}
Last Updated :
11 Jul, 2018
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