What version did you install? If it was Confluence 5.8.16 there's a bug report related to this JRE problem: https://jira.atlassian.com/browse/CONF-39852
Nevertheless, you could try setting the JRE location as it is described in that bug report.
On this documentation you can find the steps to uninstall Confluence:
Another option would be you just remove the Confluence folders and user.
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