How to modify other companies jar package

We used the other 's jar package ( authorization ) , which is supported by Jackson API documentation says (the online open source json parser ) , then we parse json part of the code on the Internet to download the most recent version of the Jackson jar package, has to do with this package .
results when using the code into the jar that company works under the package and found that it was using the old version of the Jackson library . Jackson and it is to integrate into its own bag . then I think so I used the new version of the API code can be compiled through , you have to delete the old version which includes Jackson library package , but also deleted the other functions of the company's library , I am using java decompiler sees jar inside the code.
what's a good way to do ?
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modify the order cited two libraries , which is placed in front , on the inside of the function by which to .
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I put my download the Jackson.jar folder preceded by a , "." it came in front of the other libraries , and she succeeded .