java - Error in building service in liferay 6.2 -

i new liferay , making sample application database operations. end getting errors while building services. stack trace follows:-

1. error in e:\liferay 6.2 ce ga-3\liferay-plugins-sdk-6.2\portlets\portletsessiondemo-portlet\docroot\web-inf\service\com\liferay\sample\model\userdetails.java (at line 1)     [javac]     /**     [javac]     ^     [javac] type java.util.map$entry cannot resolved. indirectly referenced required .class files     [javac] ----------     [javac] ----------     [javac] 2. error in e:\liferay 6.2 ce ga-3\liferay-plugins-sdk-6.2\portlets\portletsessiondemo-portlet\docroot\web-inf\service\com\liferay\sample\service\clpserializer.java (at line 0)     [javac]     /**     [javac]     ^     [javac] type java.io.objectinputstream cannot resolved. indirectly referenced required .class files     [javac] ----------     [javac] 2 problems (2 errors)  build failed 

any appreciated. thanx lot..

i got solution.. downgraded jdk version 1.8 1.7 , problem solved. seems service builders not compatible 1.8