Strange handling of prefix in EnviornmentPropertySource

Hi all

I just checked the following code:

https://github.com/apache/incubator-tamaya/blob/27d62b056015c5350431ad1dab3cb2be1bede821/code/spi-support/src/main/java/org/apache/tamaya/spisupport/propertysource/EnvironmentPropertySource.java#L136

For example this one:

String value = System.getProperty(TAMAYA_ENVPROPS_PREFIX);
if(value==null){
   prefix = System.getenv(TAMAYA_ENVPROPS_PREFIX);
}

Is this a bug?

I don't understand why it will loaded as SystemProperty and not safed to the member variable 'prefix'?