Help running a Java 8 program on an older version?

[darkstone]

I never have a good intro...

I have acquired a program from a different forum that requires Java version 8 to run. Now, I have my own Minecraft mod that only works on Java 6 (and I don't know how to update it). I would like to run the mentioned Java 8 program on my computer... but without corrupting my use of Java 6 for everything else.
My family, friends and I play this mod and none of us are willing to risk breaking this for the other program. I came here because I feel I can trust you guys, A) not to call me a noob, and B) to give real advice - as compared to this other forum.
So how can I do this? What I want to do is get the Java 8 program to run without making Java 8 the default program for my comp.

[MajorSlime]

Uh, just install Java 8. It will install alongside of previous versions; essentially like another program. And then, when you install it, or it updates or whatever, it may ask you to remove older versions of Java. Just say no. I would, however, keep a way to reinstall the old version of Java on hand, just in case it gets removed without you realizing it.


On another note, what Minecraft mod is it? I might be able to update it myself or find an updated version/alternative.

[darkstone]

It's actually my own mod, made custom from 1.6.4 in source.

If I install Java 8, would calling "java" from CMD do Java 6 or 8? I start Minecraft from command line.

And thank you, by the way, for answering so quick.

[MajorSlime]

Hmmm.... I'm not sure. There are two possibilities: it calls the latest version of Java installed, which would be 8 - or it calls the version whatever is running is built for. Considering the host program is Minecraft, which IS built for 8, your kinda screwed either way. Dang.

Whelp, that leaves the only other option. If you want, I'd be happy to take a loot at it for you. If you plan on keeping using it, it should be updated at some point anyways so it doesn't cause people inconvenience such has having to keep Java 6. 'Sides that, I'm curious to know what it does.

[darkstone]

Considering the host program is Minecraft, which IS built for 8...

Do you mean 1.8.8? Because my mod is based on 1.6.4. It runs on Java 7 just fine, on my mom's computer (but broke when my aunt installed JRE8).

I had considered installing JDK 8 just long enough to decompile the JRE8 program and recompile using -source 1.6. Do you think this could work, too? If installing Java 8 to stay would break Minecraft, it isn't worth it to the family.

Thank you for all your help.

[MajorSlime]

Minecraft runs just fine with Java 8. It was fully updated many versions ago, before even 1.6.4. These days, Java 7 and below is considered defunct, so you should have already upgraded to Java 8 anyways. And yes, recompling with -source 1.6 would most likely work, though there's no reason to remove JDK 8 after your done.