title: Runtime Exception on Tomcat while adding to an ArrayList
body: <p>I am dveloping a jersey based RESTful application :<br>
  so whenever i add something to my arraylist tomcat throws this error:</p>
  
  <p>The RuntimeException could not be mapped to a response, re-throwing to the HTTP container<br>
  what does this mean ?</p>
  
  <p>when diagonosing this problem i found it happens at :</p>
  
  <pre><code>mylist.add(item1);
  </code></pre>
  
  <p>why i am not able to add to arraylist ?</p>
  
  <p>My Stacktrace:</p>
  
  <pre><code>&lt;DateHere&gt; : com.sun.jersey.spi.container.ContainerResponse mapMappableContainerException
  SEVERE: The RuntimeException could not be mapped to a response, re-throwing to the HTTP container
  java.lang.NullPointerException
      at com.proj.datastorage.myclass1.&lt;init&gt;(myclass1.java:19)
      at com.proj.datastorage.myclass2.&lt;init&gt;(myclass2.java:30)
      at com.proj.front.CreateResource.newShop(CreateResource.java:109)
      at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
      at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
      at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
      at java.lang.reflect.Method.invoke(Unknown Source)
      at com.sun.jersey.spi.container.JavaMethodInvokerFactory$1.invoke(JavaMethodInvokerFactory.java:60)
      at com.sun.jersey.server.impl.model.method.dispatch.AbstractResourceMethodDispatchProvider$VoidOutInvoker._dispatch(AbstractResourceMethodDispatchProvider.java:167)
      at com.sun.jersey.server.impl.model.method.dispatch.ResourceJavaMethodDispatcher.dispatch(ResourceJavaMethodDispatcher.java:75)
      at com.sun.jersey.server.impl.uri.rules.HttpMethodRule.accept(HttpMethodRule.java:302)
      at com.sun.jersey.server.impl.uri.rules.RightHandPathRule.accept(RightHandPathRule.java:147)
      at com.sun.jersey.server.impl.uri.rules.ResourceClassRule.accept(ResourceClassRule.java:108)
      at com.sun.jersey.server.impl.uri.rules.RightHandPathRule.accept(RightHandPathRule.java:147)
      at com.sun.jersey.server.impl.uri.rules.RootResourceClassesRule.accept(RootResourceClassesRule.java:84)
      at com.sun.jersey.server.impl.application.WebApplicationImpl._handleRequest(WebApplicationImpl.java:1511)
      at com.sun.jersey.server.impl.application.WebApplicationImpl._handleRequest(WebApplicationImpl.java:1442)
      at com.sun.jersey.server.impl.application.WebApplicationImpl.handleRequest(WebApplicationImpl.java:1391)
      at com.sun.jersey.server.impl.application.WebApplicationImpl.handleRequest(WebApplicationImpl.java:1381)
      at com.sun.jersey.spi.container.servlet.WebComponent.service(WebComponent.java:416)
      at com.sun.jersey.spi.container.servlet.ServletContainer.service(ServletContainer.java:538)
      at com.sun.jersey.spi.container.servlet.ServletContainer.service(ServletContainer.java:716)
      at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
      at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
      at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
      at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
      at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
      at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
      at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
      at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
      at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:293)
      at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:849)
      at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583)
      at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:454)
      at java.lang.Thread.run(Unknown Source)
  </code></pre>