How to change Java version used by TOMCAT?

I have Java 1.6 and Tomcat 5.5 installed on my system.

But Tomcat 5.5 accesses Java 1.5 and hence as the outcome I get the error Bad version number in .class file while executing java code with JSP.

How can I change the Tomcat version to Java 1.6?

UPDATE

I tried changing the JVM that the tomcat5w.exe is pointing to the version 1.6 and now I am out of the Bad version in .class file error. But now, I get the following error.

exceptionorg.apache.jasper.JasperExceptionorg.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:498)org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:411)org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:308)org.apache.jasper.servlet.JspServlet.service(JspServlet.java:259)javax.servlet.http.HttpServlet.service(HttpServlet.java:729)root causejava.lang.NullPointerExceptionmyfirst.SearchLink.checkURL(SearchLink.java:20)org.apache.jsp.Test_jsp._jspService(Test_jsp.java:52)org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:98)javax.servlet.http.HttpServlet.service(HttpServlet.java:729)org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:369)org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:308)org.apache.jasper.servlet.JspServlet.service(JspServlet.java:259)javax.servlet.http.HttpServlet.service(HttpServlet.java:729)

What might be the root cause?