java UnsupportedClassVersionError

While deploy java code into tomcat, it thrown exception as follows

SEVERE: Exception starting filter struts
java.lang.UnsupportedClassVersionError: Bad version number in .class file (unable to load class jcaptcha4struts2.core.actions.support.CaptchaImageResult)
at org.apache.catalina.loader.WebappClassLoader.findClassInternal( WebappClassLoader.java:1851)
at org.apache.catalina.loader.WebappClassLoader.findClass( WebappClassLoader.java:890)
.......
.......
at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:288)
at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:413)
17 Mar, 2009 1:29:25 PM org.apache.catalina.core.ApplicationContext log
INFO: Closing Spring root WebApplicationContext

The problem is version conflict [development machine java version is 1.5 but machine where i deploy has the 1.6 version]

To fix this problem we need to install java-1.6 version in the deployment machine.