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You can set up your Eclipse so that identations are done in tabs rather than spaces. See convert spaces to tabs. In older versions of Eclipse, the button is "Show" rather than "Edit". Here is a sample screenshot http://ofbizwiki.go-integral.com/attach/FAQ27/eclipse_spaces_for_tabs.png
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If you want some scripts to help you check and clean up tabs in your files, go to http://www.opensourcestrategies.com/ofbiz/downloads.php
. I'm told by the real Unix gurus that "this takes one line in sed." Yeah, I've heard that one before...