这是commons-lang-2.5.jar下载，解决java.lang.NoClassDefFoundError: org/apache/commons/lang/StringUtils异常。
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commons-lang-2.5.jar是日常编程中必不可少的一个jar包，在日常java编程中，经常会使用到commons-lang.jar包，还没有准备commons-lang.jar包的用户马上下载使用吧。
apache的工具包，包含stringutil等实用工具类-apache toolkit， including stringutil and other utility classes.
