确认安装了想要的版本，用下列命令查看当前安装了那些版本的java
$ sudo update-java-alternatives -l
java-1.5.0-sun 53 /usr/lib/jvm/java-1.5.0-sun
java-6-sun 63 /usr/lib/jvm/java-6-sun
选择1.5
$ sudo update-java-alternatives -s java-1.5.0-sun出处http://stackoverflow.com/questions/672795/how-do-i-downgrade-java-from-1-6-0-to-1-5-0-in-ubuntu