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Java Hashtable keys() Method with Example

Hashtable Class keys() method: Here, we are going to learn about the keys() method of Hashtable Class with its syntax and example.
Submitted by Preeti Jain, on February 17, 2020

Hashtable Class keys() method

• keys() method is available in java.util package.
• keys() method is used to returns keys of an enumeration in this Hashtable.
• keys() method is a non-static method, it is accessible with the class object only and if we try to access the method with the class name then we will get an error.
• keys() method does not throw an exception at the time of returning keys of an enumeration.

Syntax:

    public Enumeration keys();

Parameter(s):

• It does not accept any parameter.

Return value:

The return type of the method is Enumeration, it returns set of keys of an enumeration in this Hashtable.

Example:

// Java program to demonstrate the example 
// of Enumeration keys() method of Hashtable 

import java.util.*;

public class KeysOfHashtable {
    public static void main(String[] args) {
        //Instantiate a hashtable object  
        Hashtable ht = new Hashtable();

        // By using put() method is to
        // add the linked values in an
        // Hashtable ht
        ht.put(10, "C");
        ht.put(20, "C++");
        ht.put(30, "JAVA");
        ht.put(40, "PHP");
        ht.put(50, "SFDC");

        // Display Hashtable
        System.out.println("Hashtable: " + ht);

        // By using keys() method is to
        // returns the enumeration of all the
        // key exists in this Hashtable

        System.out.println("ht.keys(): ");
        for (Enumeration en = ht.keys(); en.hasMoreElements();) {
            System.out.println(en.nextElement());
        }
    }
}

Output

Hashtable: {10=C, 20=C++, 30=JAVA, 40=PHP, 50=SFDC}
ht.keys(): 
10
20
30
40
50