Jdom resolve the server returns a changed XML

Jdom resolve the server returns a change in XML, the same root , which nodes may change sometimes there , sometimes no . How judgment and analysis, basic analytical methods I know , do not know how to judge . There is a node with a child node with the same name but a different number of attributes , how to remove judge not ? Find Great God
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direct analysis like, but also to determine what
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direct analysis will complain ah java.lang.NullPointerException. . . To determine whether it
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been resolved. . . if judgment is that the child node if ( root get child nodes ! = null) { content } performed on the line. . . In the Element front to make a judgment
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Thank you for your reply and give you