As part of the Property Map article

PropertiesExample.java

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.Properties;

public class PropertiesExample {
    public static void main(String[] args) {
        // Defining a properties instance
        System.out.println("--- Defining a properties instance ---");
        Properties props = new Properties();
        props.setProperty("version", "1.4.2");
        props.setProperty("author", "Joe Bloggs");

        // Saving to a file
        System.out.println("\n--- Saving to a file ---");
        try {
            FileOutputStream out = new FileOutputStream("conf.properties");
            props.store(out, "Configuration properties");
        } catch (IOException e) {
            e.printStackTrace();
        }

        // Reading from a file
        System.out.println("\n--- Reading from a file ---");
        Properties loaded = new Properties();
        try {
            FileInputStream in = new FileInputStream("conf.properties");
            loaded.load(in);

            // Retrieving value (no default)
            String author = loaded.getProperty("author");
            System.out.println("Author: " + author);

            // Retrieving value with a default
            String noKey = loaded.getProperty("location", "Stockholm");
            System.out.println("Default key: " + noKey);

        } catch (IOException e) {
            e.printStackTrace();
        }

        // Retrieving values: default properties with a secondary property map
        System.out.println("\n--- Retrieving values using a secondary property map---");
        Properties defaultProps = new Properties();
        defaultProps.setProperty("version", "v1.0.0");
        defaultProps.setProperty("author", "Clark Kent");

        Properties props2 = new Properties(defaultProps);

        String version = props2.getProperty("version");
        System.out.println("Version: " + version);

    }
}