Java Properties file, how to set only 1 property

Question

am with an application that works with Properties configuration files.

Imagine that I have a file with 100 properties and in a certain part of my code, I want to rewrite only 1 of these properties, have to do it without losing the others that are already there ?

Below follows code I am testing and trying to get the result above.

public class propriedades {

public static void main(String[] args) {

    Properties properties = new Properties();

    // setando as propriedades(key) e os seus valores(value)
    properties.setProperty("jdbc.user", "sysdba1");
    properties.setProperty("jdbc.pass", "masterkey");

    try {
        // Criamos um objeto FileOutputStream
        FileOutputStream fos = new FileOutputStream("C:/jdbc.properties");
        // grava os dados no arquivo
        properties.store(fos, "FILE JDBC PROPERTIES:");
        // fecha o arquivo
        fos.close();
    } catch (IOException ex) {
        System.out.println(ex.getMessage());
        ex.printStackTrace();
    }
}

}