How are you trying to run the jar? With MCP's "startclient.bat" file? Or with an external launcher? Are you simply taking the compiled jar from MCP (which is not a complete working jar) or combining the reobfuscated files with a vanilla jar (the latter being the proper way)? What Java version are you using? Alpha was written for Java 5, even as recently as 1.11 only Java 6 was required and newer versions of Java, 9 in particular, made major changes to the internal workings so many other applications have issues. Even Java 7 (and since) causes issues with older versions unless you add "-Djava.util.Arrays.useLegacyMergeSort=true" to the JVM arguments (this causes a different issue than what you have but should still be done),
I am using MCP version 2.5, And everything went well until I tried to test my game.
It said:
Me being new, I tried an alternative to start Minecraft. (They're usually dangerous, Especially if you modify the worldgen.)
I tried recompiling and then running the .jar file. It just complained about the manifest.
I tried googling for help, But that didn't work.
So now I'm here creating a thread. Does anybody have any ideas?
Update: I think I've solved that problem, But now it says this:
Now what? (I've tried adding a manifest but failed)
How are you trying to run the jar? With MCP's "startclient.bat" file? Or with an external launcher? Are you simply taking the compiled jar from MCP (which is not a complete working jar) or combining the reobfuscated files with a vanilla jar (the latter being the proper way)? What Java version are you using? Alpha was written for Java 5, even as recently as 1.11 only Java 6 was required and newer versions of Java, 9 in particular, made major changes to the internal workings so many other applications have issues. Even Java 7 (and since) causes issues with older versions unless you add "-Djava.util.Arrays.useLegacyMergeSort=true" to the JVM arguments (this causes a different issue than what you have but should still be done),
TheMasterCaver's First World - possibly the most caved-out world in Minecraft history - includes world download.
TheMasterCaver's World - my own version of Minecraft largely based on my views of how the game should have evolved since 1.6.4.
Why do I still play in 1.6.4?