Yes you can combine google Combochart with GWT easily. with the same jar that you mentioned. follow this link..
The error that you are facing is sounds like jar version issue.
문제
Anyone knows if its posible to use the Google ComboChart with GWT . I tried using the wrapper in GWT Visualization Wrapper but I get the error sun.misc.InvalidJarIndexException: Invalid index
Im using the jar found in GWT official jar
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Yes you can combine google Combochart with GWT easily. with the same jar that you mentioned. follow this link..
The error that you are facing is sounds like jar version issue.