The JAVA_HOME environment variable is not defined

启动命令如下：
login: sgqgweb
Password:
Last login: Wed Nov 11 07:37:43 from bogon
[sgqgweb@www ~]$ ls
???????系?button.swf    jakarta-tomcat-5.0.30.tgz  sgqgweb
Desktop                jdk1.5.0_06                sgqgweb.tar
jakarta-tomcat-5.0.30  jdk1.5.0_06.tgz            sgqgweb.tgz
[sgqgweb@www ~]$ cd jakar*
[sgqgweb@www jakarta-tomcat-5.0.30]$ ls
bin     conf     logs    RELEASE-NOTES  server   work
common  LICENSE  NOTICE  RUNNING.txt    webapps
[sgqgweb@www jakarta-tomcat-5.0.30]$ cd bin
[sgqgweb@www bin]$ ls
bootstrap.jar            setclasspath.bat
catalina.50.bat          setclasspath.sh
catalina.50.sh           shutdown.bat
catalina.bat             shutdown.sh
catalina.sh              shutdown-using-launcher.bat
catalina.xml             shutdown-using-launcher.sh
commons-daemon.jar       startup.bat
commons-launcher.jar     startup.sh
commons-logging-api.jar  startup-using-launcher.bat
contrib                  startup-using-launcher.sh
cpappend.bat             tomcat5.exe
digest.bat               tomcat5w.exe
digest.sh                tool-wrapper.bat
jmx.jar                  tool-wrapper.sh
jsvc.tar.gz              tool-wrapper-using-launcher.bat
LauncherBootstrap.class  tool-wrapper-using-launcher.sh
launcher.properties      version.bat
nohup.out                version.sh
service.bat
[sgqgweb@www bin]$ ./catalina.sh start
The JAVA_HOME environment variable is not defined
This environment variable is needed to run this program
[sgqgweb@www bin]$
报错如下：
The JAVA_HOME environment variable is not defined
This environment variable is needed to run this program
解决办法：