synchronized方法和同步块的作用范围;synchronized(this)和synchronized(obj)的区别
参考资源:http://www.cnblogs.com/oracleDBA/archive/2010/05/22/1741642.htmlhttp://www.cnblogs.com/highriver/archive/2011/12/18/2291965.htmlhttp://www.2cto.com/kf/200906/39293.htmlhttp://wangym.iteye.com/blo