遍历枚举

 * Implementation Notes:
 * 1. String prefix = configName + ".";
 * 2. Create Properties instance for inner configuration:
 *      result = new Properties();
 * 3. For each (String key; String value) from properties do:
 *      3.1. If key.startsWith(prefix) then
 *              3.1.1. Remove the prefix from the key:
 *                         String newKey = key.substring(prefix.length());
 *              3.1.2. Put key/value pair to the inner configuration:
 *                         result.put(newKey, value);
 * 4. Return result.
 * @param configName the name of the inner configuration
 * @param properties the properties with the main configuration
 * @return the Properties container with the extracted inner configuration (not null)
*/
public static Properties getSubConfiguration(Properties properties, String configName) {
    String prefix = configName + ".";
    Properties result = new Properties();
    Enumeration enumer = properties.keys();
    while(enumer.hasMoreElements()) {
        String key = (String) enumer.nextElement();
        String value = properties.getProperty(key);
        if(key.startsWith(prefix)){
            String newKey = key.substring(prefix.length());
            result.put(newKey, value);
        }
    }
    return result;
}