How to resolve this issue.

HTTP Status 500 - java.lang.NullPointerException

type Exception report

message java.lang.NullPointerException

description The server encountered an internal error that prevented it from fulfilling this request.

exception

javax.servlet.ServletException: java.lang.NullPointerException javax.faces.webapp.FacesServlet.service(FacesServlet.java:671) org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:51) 

root cause

javax.faces.el.EvaluationException: java.lang.NullPointerException javax.faces.component.MethodBindingMethodExpressionAdapter.invoke(MethodBindingMethodExpressionAdapter.java:101) com.sun.faces.application.ActionListenerImpl.processAction(ActionListenerImpl.java:102) javax.faces.component.UICommand.broadcast(UICommand.java:315) javax.faces.component.UIViewRoot.broadcastEvents(UIViewRoot.java:790) javax.faces.component.UIViewRoot.processApplication(UIViewRoot.java:1282) com.sun.faces.lifecycle.InvokeApplicationPhase.execute(InvokeApplicationPhase.java:81) com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101) com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:198) javax.faces.webapp.FacesServlet.service(FacesServlet.java:658) org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:51) 

root cause

java.lang.NullPointerException java.base/java.io.StreamTokenizer.(StreamTokenizer.java:248) weka.core.converters.ArffLoader$ArffReader.(ArffLoader.java:159) com.jsf.bootstrap.StudentBean.testWeather(StudentBean.java:281) java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:78) java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) java.base/java.lang.reflect.Method.invoke(Method.java:567) org.apache.el.parser.AstValue.invoke(AstValue.java:278) org.apache.el.MethodExpressionImpl.invoke(MethodExpressionImpl.java:274) com.sun.faces.facelets.el.TagMethodExpression.invoke(TagMethodExpression.java:105) javax.faces.component.MethodBindingMethodExpressionAdapter.invoke(MethodBindingMethodExpressionAdapter.java:87) com.sun.faces.application.ActionListenerImpl.processAction(ActionListenerImpl.java:102) javax.faces.component.UICommand.broadcast(UICommand.java:315) javax.faces.component.UIViewRoot.broadcastEvents(UIViewRoot.java:790) javax.faces.component.UIViewRoot.processApplication(UIViewRoot.java:1282) com.sun.faces.lifecycle.InvokeApplicationPhase.execute(InvokeApplicationPhase.java:81) com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101) com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:198) javax.faces.webapp.FacesServlet.service(FacesServlet.java:658) org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:51) 

note The full stack trace of the root cause is available in the Apache Tomcat/7.0.47 logs.

Apache Tomcat/7.0.47