Implemented `concat` in Java for optimization
Moved Java concat to correct directory
Fixed test.sh script
Otherwise this error may occur: Class not found: org.eclipse.jdt.core.JDTCompilerAdapter
Updated concat with Vlad's implementation.
It's not measurably faster, but simpler and might be faster in some situations.
Merge pull request #12 from Virtlink/java-bootstrap

Implemented `concat` in Java for optimization