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Java Dictionary keys() Method with Example

Dictionary Class keys() method: Here, we are going to learn about the keys() method of Dictionary Class with its syntax and example.
Submitted by Preeti Jain, on February 13, 2020

Dictionary Class keys() method

• keys() method is available in java.util package.
• keys() method is used to get sets of keys of an Enumeration in this dictionary.
• keys() method is a non-static method, it is accessible with the class object 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 abstract Enumeration keys();

Parameter(s):

• It does not accept any parameter.

Return value:

The return type of this method is Enumeration, it returns sets of keys of an enumeration in this dictionary.

Example:

// Java program is to demonstrate the example of
// keys() method of Dictionary

import java.util.*;

public class KeysOfDictionary {
    public static void main(String[] args) {

        // Instantiate a Hashtable object
        Dictionary dictionary = new Hashtable();

        // By using put() method is to
        // add an elements in Hashtable 
        dictionary.put(1, "C");
        dictionary.put(2, "C++");
        dictionary.put(3, "JAVA");
        dictionary.put(4, "PHP");
        dictionary.put(5, "SFDC");

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

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

Output

dictionary.keys(): 
5
4
3
2
1