Properties keys() method in Java with Examples

The keys() method of Properties class is used to get the enumeration of the keys in this Properties object. This enumeration can be used to traverse and iterate the keys sequentially.

Syntax:

public Enumeration keys()

Parameters: This method accepts no parameters

Returns: This method returns an Enumeration of the keys of this Properties object sequentially.

Below programs show the implementation of int keys() method.

Program 1:

// Java code to show the implementation of
// keys() method

import java.util.*;
public class GfG {

    // Main method
    public static void main(String[] args)
    {

        // Create a properties and add some values
        Properties properties = new Properties();
        properties.put("Pen", 10);
        properties.put("Book", 500);
        properties.put("Clothes", 400);
        properties.put("Mobile", 5000);

        // Print Properties details
        System.out.println("Properties: "
                           + properties.toString());

        // Creating an empty enumeration to store
        Enumeration enu = properties.keys();

        System.out.println("The enumeration of keys are:");

        // Displaying the Enumeration
        while (enu.hasMoreElements()) {
            System.out.println(enu.nextElement());
        }
    }
}

Output:

Properties: {Book=500, Mobile=5000, Pen=10, Clothes=400}
The enumeration of keys are:
Book
Mobile
Pen
Clothes

Program 2:

// Java program to demonstrate
// keys() method.

import java.util.*;

public class GFG {

    // Main method
    public static void main(String[] args)
    {

        // Create a properties and add some values
        Properties properties = new Properties();

        // Inserting elements into the properties
        properties.put("Geeks", 10);
        properties.put("4", 15);
        properties.put("Geeks", 20);
        properties.put("Welcomes", 25);
        properties.put("You", 30);

        // Print Properties details
        System.out.println("Current Properties: "
                           + properties.toString());

        // Creating an empty enumeration to store
        Enumeration enu = properties.keys();

        System.out.println("The enumeration of keys are:");

        // Displaying the Enumeration
        while (enu.hasMoreElements()) {
            System.out.println(enu.nextElement());
        }
    }
}

Output:

Current Properties: {You=30, Welcomes=25, 4=15, Geeks=20}
The enumeration of keys are:
You
Welcomes
4
Geeks

References: https://docs.oracle.com/javase/9/docs/api/java/util/Properties.html#keys–