Java Properties class

The java.util.Properties class in Java is a part of the Java Standard Library and is used to manage and manipulate configuration or settings information in key-value pairs. It is commonly used to load and save configuration data from files or other data sources.

The Properties class extends the Hashtable class and provides some additional methods for working specifically with key-value pairs in the context of configuration. Each key and value in a Properties object is a String, and they are usually used to represent properties of a system or application.

Here are some key features and methods of the Properties class:

1. Loading Properties from Files:
   You can load properties from a file using methods like load(InputStream) or load(Reader). The properties file should be in a key=value format.
2. Storing Properties to Files:
   You can store properties to a file using methods like store(OutputStream, String) or store(Writer, String). This allows you to save configuration changes back to the file.
3. Getting and Setting Properties:
   You can get property values using the getProperty(String key) method. If a property doesn’t exist, you can provide a default value. You can set properties using the setProperty(String key, String value) method.
4. Enumeration of Properties:
   You can obtain an enumeration of all keys using the propertyNames() method, which allows you to iterate through the keys and retrieve their values.

Here’s a simple example of using the Properties class to load and store configuration data:

import java.io.*;
import java.util.Properties;

public class PropertiesExample {
    public static void main(String[] args) {
        Properties properties = new Properties();

        try (InputStream input = new FileInputStream("config.properties")) {
            properties.load(input);

            // Getting property values
            String username = properties.getProperty("username");
            String password = properties.getProperty("password");

            System.out.println("Username: " + username);
            System.out.println("Password: " + password);
        } catch (IOException e) {
            e.printStackTrace();
        }

        try (OutputStream output = new FileOutputStream("config.properties")) {
            // Setting property values
            properties.setProperty("username", "myusername");
            properties.setProperty("password", "mypassword");

            properties.store(output, "Updated configuration");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

In this example, the Properties class is used to load and store configuration data from a properties file named “config.properties”. The load method is used to read properties from the file, and the store method is used to update and save properties back to the file.

Keep in mind that while Properties is a straightforward way to manage configuration data, for more complex scenarios, you might consider using more advanced configuration management libraries.