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摘要：
About hashcode and equalsRule 1: If override equals(), and should override hashcode(), make sure if two object 'equals', then them should have same hashcode. actual, you also break the rule, the compile will pass, but it maybe cause some bugs.Rule 2: If two object not equals, then they hashc 阅读全文
posted @ 2014-03-12 20:53 钟悍 阅读(195) 评论(0) 推荐(0) 编辑
摘要：
Many relation database handle a JDBC sql query in blew four steps:1, parse the incoming sql2, compile the sql3, plan/ optimize the sql.4, execute the sql and return dataA Statement will always procceed the four steps for each sql quer sent to the database. A PrepareStatement will pre-execute the ste 阅读全文
posted @ 2014-03-12 20:40 钟悍 阅读(281) 评论(0) 推荐(0) 编辑
摘要：
1, unChecked Exception, represent a defect in programmer(bugs). should inherit RuntimeException or Error.Unchecked runtime exceptions represent conditions that, generally speaking, reflect errors in your program's logic and cannot be reasonably recovered from at run time.2, checked Exception,rep 阅读全文
posted @ 2014-03-12 20:00 钟悍 阅读(235) 评论(0) 推荐(0) 编辑 |
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