The java.util.Hashtable.remove() is an inbuilt method of Hashtable class and is used to remove the mapping of any particular key from the table. It basically removes the values for any particular key in the Table.
Syntax:
Hash_Table.remove(Object key)
Parameters: The method takes one parameter key whose mapping is to be removed from the Table.
Return Value: The method returns the value that was previously mapped to the specified key if the key exists else the method returns NULL.
Below programs illustrates the working of java.util.Hashtable.remove() method:
Program 1: When passing an existing key.
// Java code to illustrate the remove() method import java.util.*;
public class Hash_Table_Demo {
public static void main(String[] args)
{
// Creating an empty Hashtable
Hashtable<Integer, String> hash_table =
new Hashtable<Integer, String>();
// Inserting elements into the table
hash_table.put( 10 , "Geeks" );
hash_table.put( 15 , "4" );
hash_table.put( 20 , "Geeks" );
hash_table.put( 25 , "Welcomes" );
hash_table.put( 30 , "You" );
// Displaying the Hashtable
System.out.println( "Initial Table is: " + hash_table);
// Removing the existing key mapping
String returned_value = (String)hash_table.remove( 20 );
// Verifying the returned value
System.out.println( "Returned value is: " + returned_value);
// Displaying the new table
System.out.println( "New table is: " + hash_table);
}
} |
Initial Table is: {10=Geeks, 20=Geeks, 30=You, 15=4, 25=Welcomes} Returned value is: Geeks New table is: {10=Geeks, 30=You, 15=4, 25=Welcomes}
Program 2: When passing a new key.
// Java code to illustrate the remove() method import java.util.*;
public class Hash_Table_Demo {
public static void main(String[] args)
{
// Creating an empty Hashtable
Hashtable<Integer, String> hash_table =
new Hashtable<Integer, String>();
// Inserting mappings into the table
hash_table.put( 10 , "Geeks" );
hash_table.put( 15 , "4" );
hash_table.put( 20 , "Geeks" );
hash_table.put( 25 , "Welcomes" );
hash_table.put( 30 , "You" );
// Displaying the Hashtable
System.out.println( "Initial table is: " + hash_table);
// Removing the new key mapping
String returned_value = (String)hash_table.remove( 50 );
// Verifying the returned value
System.out.println( "Returned value is: " + returned_value);
// Displaying the new table
System.out.println( "New table is: " + hash_table);
}
} |
Initial table is: {10=Geeks, 20=Geeks, 30=You, 15=4, 25=Welcomes} Returned value is: null New table is: {10=Geeks, 20=Geeks, 30=You, 15=4, 25=Welcomes}
Note: The same operation can be performed with any type of variation and combination of different data types.