How to overwrite one property in .properties without overwriting the whole file?

Question

Basically, I have to overwrite a certain property in a .properties file through a Java app, but when I use Properties.setProperty() and Properties.Store() it overwrites the

Answer 1

public class PropertiesXMLExample {
    public static void main(String[] args) throws IOException {

    // get properties object
    Properties props = new Properties();

    // get path of the file that you want
    String filepath = System.getProperty("user.home")
            + System.getProperty("file.separator") +"email-configuration.xml";

    // get file object
    File file = new File(filepath);

    // check whether the file exists
    if (file.exists()) {
        // get inpustream of the file
        InputStream is = new FileInputStream(filepath);

        // load the xml file into properties format
        props.loadFromXML(is);

        // store all the property keys in a set 
        Set names = props.stringPropertyNames();

        // iterate over all the property names
        for (Iterator i = names.iterator(); i.hasNext();) {
            // store each propertyname that you get
            String propname = i.next();

            // set all the properties (since these properties are not automatically stored when you update the file). All these properties will be rewritten. You also set some new value for the property names that you read
            props.setProperty(propname, props.getProperty(propname));
        }

        // add some new properties to the props object
        props.setProperty("email.support", "donot-spam-me@nospam.com");
        props.setProperty("email.support_2", "donot-spam-me@nospam.com");

       // get outputstream object to for storing the properties into the same xml file that you read
        OutputStream os = new FileOutputStream(
                System.getProperty("user.home")
                        + "/email-configuration.xml");

        // store the properties detail into a pre-defined XML file
        props.storeToXML(os, "Support Email", "UTF-8");

        // an earlier stored property
        String email = props.getProperty("email.support_1");

        System.out.println(email);
      }
   }
}

The output of the program would be:

support@stackoverflow.com