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Hashtable keys() Method in Java
  • Last Updated : 28 Jun, 2018

The java.util.Hashtable.keys() method of Hashtable class in Java is used to get the enumeration of the keys present in the hashtable.

Syntax:

Enumeration enu = Hash_table.keys()

Parameters: The method does not take any parameters.

Return value: The method returns an enumeration of the keys of the Hashtable.

Below programs are used to illustrate the working of the java.util.Hashtable.keys() method:
Program 1:






// Java code to illustrate the keys() 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("The Table is: " + hash_table);
  
        // Creating an empty enumeration to store
        Enumeration enu = hash_table.keys();
  
        System.out.println("The enumeration of keys are:");
  
        // Displaying the Enumeration
        while (enu.hasMoreElements()) {
            System.out.println(enu.nextElement());
        }
    }
}
Output:
The Table is: {10=Geeks, 20=Geeks, 30=You, 15=4, 25=Welcomes}
The enumeration of keys are:
10
20
30
15
25

Program 2:




// Java code to illustrate the keys() method
import java.util.*;
  
public class Hash_Table_Demo {
    public static void main(String[] args)
    {
  
        // Creating an empty Hashtable
        Hashtable<String, Integer> hash_table = 
                         new Hashtable<String, Integer>();
  
        // Inserting elements into the table
        hash_table.put("Geeks", 10);
        hash_table.put("4", 15);
        hash_table.put("Geeks", 20);
        hash_table.put("Welcomes", 25);
        hash_table.put("You", 30);
  
        // Displaying the Hashtable
        System.out.println("The Table is: " + hash_table);
  
        // Creating an empty enumeration to store
        Enumeration enu = hash_table.keys();
  
        System.out.println("The enumeration of keys are:");
  
        // Displaying the Enumeration
        while (enu.hasMoreElements()) {
            System.out.println(enu.nextElement());
        }
    }
}
Output:
The Table is: {You=30, Welcomes=25, 4=15, Geeks=20}
The enumeration of keys are:
You
Welcomes
4
Geeks

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