[root@localhost ~]# vim /etc/profile
export JAVA_HOME=/usr/java/jdk1.6.0_45
export PATH=$JAVA_HOME/bin:$PATH 
export CLASSPATH=.:$JAVA_HOME/lib/dt.jar:$JAVA_HOME/lib/tools.jar

[root@localhost ~]# source /etc/profile
[root@localhost ~]# java -version