I got the following errors, starting from a blank slate (freshly installed SDK and Eclipse, with those installations verified by running Hello World), and then downloaded battlecode-scaffold 0.0.2.
First, I got exactly the same error as leroygankins reported. fyzyx's fix (a new JAVA_HOME user variable and system variable on This PC > Properties > Advanced System Settings > Advanced > Environment Variables) plus restarting my computer cleared that error.
Now when trying build.xml > Run As > Ant Build > Update battlecode , I get a new set of errors. The first one is [javac] C:\Users\Adam\Downloads\battlecode-scaffold-master\battlecode-scaffold-master\src\examplefuncsplayer\RobotPlayer.java:3: error: package battlecode.common does not exist .
I suspect that this is the error kazimuth posted in the first post: when I go to Project / Properties / Java Build Path / Libraries , all the jars are marked as missing. But when I click "Add JARs...", I can't find a lib directory. If I instead click "Add External JARs..." and go to battlecode-scaffold-master, there's a lib folder, but it's empty. I'm out of ideas.