Properties keySet() method in Java with Examples

The keySet() method of Properties class is used to create a set out of the key elements contained in the Properties. It basically returns a set view of the keys or we can create a new set and store the key elements in them.

Syntax:

public Set keySet()

Parameters: This method accepts no parameters

Returns: This method returns a Set view of the keys contained in this Properties object.

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

Program 1:

// Java code to show the implementation of 
// keySet() 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()); 
  
        System.out.println("keySet: "
                           + properties.keySet()); 
    } 
} 

Output:

Properties: {Book=500, Mobile=5000, Pen=10, Clothes=400}
keySet: [Book, Mobile, Pen, Clothes]

Program 2:

// Java program to demonstrate 
// keySet() 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()); 
  
        System.out.println("keySet: "
                           + properties.keySet()); 
    } 
} 

Output:

Current Properties: {You=30, Welcomes=25, 4=15, Geeks=20}
keySet: [You, Welcomes, 4, Geeks]

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

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