Fundamental programming skills are the same in any language may it be Ruby, PHP, or C, so if I were you I'd learn Ruby (or maybe Python; I prefer Ruby though) in those 8 months and then take a good programming class in collage to advance to Java/C. For a average startup a low level language such as Java or C will be pretty useless, you'll do 99% of things in something like Ruby, Python or even PHP.
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Fundamental programming skills are the same in any language may it be Ruby, PHP, or C, so if I were you I'd learn Ruby (or maybe Python; I prefer Ruby though) in those 8 months and then take a good programming class in collage to advance to Java/C. For a average startup a low level language such as Java or C will be pretty useless, you'll do 99% of things in something like Ruby, Python or even PHP.