How to properly save a properties file with special characters

Question

I have a property file like this:

[flags]
prop1=value
prop2=value
[patterns]
prop3=#.00
prop4=###,##0.00
[other]
prop5=value

When I process the file, not only the pound signs are escaped (#), but all my properties are out of order.

my code is something like this:

Properties props = new Properties();

FileInputStream in = null;
try
{
   in = new FileInputStream(PROP_FILE);
   Reader reader = new InputStreamReader(in, StandardCharsets.UTF_8);
   props.load(reader);
}
catch (IOException e)
{
   // log exception
}
finally
{
   if (in != null)
   {
      try
      {
         in.close();
      }
      catch (IOException e)
      {
         // log exception
      }
   }
}

props.setProperty("prop5", "otherValue");
try
{
   OutputStreamWriter w = new OutputStreamWriter(new FileOutputStream(INI_FILE), StandardCharsets.UTF_8);
   props.store(w, null);
}
catch (IOException e)
{
   // log exception
}

I am using props.store() because I do not know of another way to save the properties file after props.setProperty() is called.

Answer 1

All the credit goes to Jon Skeet for pointing out that Java Properties are not meant to be used this way, and that what I needed was a Windows-style .ini file. Because of this suggestion, I remember I used ini4j many years ago and that is what I needed to use in this case.

The solution is quite simple:

try
{
   Wini ini = new Wini(new File(PROP_FILE));
   ini.put("others", "prop5", value); // "others" is the section, "prop5" the key, and "value" is self-explanatory.
   ini.store(); // INI file is saved
}
catch (IOException e)
{
   // log problem... do whatever!
}

When using ini4j to save, my properties are preserved in sections, and the order of properties is preserved, and special characters (like #) are not escaped; which addresses ALL of the issues.