Help

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So I'm running the latest version of windows and everything, and when I download Java it shows I downloaded it and everything. But when I try to open a java file (optifine for minecraft) I get an error saying that:

Unable to install Java

There are errors in the following switches:

*the file i tried to open name*

check that the commands are valid and try again

I also checked my default apps and it says that for JAR files the default is java.