小菜目前刚学spark，安装spark的操作系统环境是ubuntu 12.0.4。安装的scala是scala-2.9.1.final.tgz。配置好环境变量后，通过git clone git://github.com/aparch/spark.git下载spark源代码后，执行命令sbt/sbt update complie,出现信息如下：
NOTE: The sbt/sbt script has been relocated to build/sbt.
Please update references to point to the new location.
Invoking 'build/sbt update compile' now ...
/root/spark/build/sbt-launch-lib.bash: line 84: java: command not found
查了半天不知道是什么原因，恳请各位大侠帮忙看看。
