in src/main/java/org/apache/commons/configuration2/CombinedConfiguration.java [293:318]
public void addConfiguration(final Configuration config, final String name, final String at) {
if (config == null) {
throw new IllegalArgumentException("Added configuration must not be null!");
}
beginWrite(true);
try {
if (name != null && namedConfigurations.containsKey(name)) {
throw new ConfigurationRuntimeException("A configuration with the name '" + name + "' already exists in this combined configuration!");
}
final ConfigData cd = new ConfigData(config, name, at);
if (getLogger().isDebugEnabled()) {
getLogger().debug("Adding configuration " + config + " with name " + name);
}
configurations.add(cd);
if (name != null) {
namedConfigurations.put(name, config);
}
invalidateInternal();
} finally {
endWrite();
}
registerListenerAt(config);
}