兩種單例模式

現需要將XmlConfigReader.java做成單例模式，提供以下兩種方法

 

1. 餓漢式
   
   private static XmlConfigReader instance = new XmlConfigReader(); private XmlConfigReader() { } public static XmlConfigReader getInstance() { return instance; }
   
2. 懶漢式
   
   private static XMLConfigReader instance = null; private XMLConfigReader(){ } public static synchronized XMLConfigReader getXmlConfigReader(){ if (instance == null) { instance = new XMLConfigReader(); } return instance; }