两种单例模式

现需要将XmlConfigReader.java做成单例模式，提供以下两种方法

 

1. 饿汉式
   
   private static XmlConfigReader instance = new XmlConfigReader();private XmlConfigReader() {}public static XmlConfigReader getInstance() {return instance;}
   
2. 懒汉式
   
   private static XMLConfigReader instance = null;private XMLConfigReader(){}public static synchronized XMLConfigReader getXmlConfigReader(){if (instance == null) {instance = new XMLConfigReader();}return instance;}