title: JAVA java.util.ConcurrentModificationException:null Exception
body: <p>I am working on my code and getting "java.util.ConcurrentModificationException". I googled it and also know that such error comes only when you try to modify on-going iterative variable, which I don't feel in my case. Below is my code.</p>
  
  <pre><code>// This line is having an error
  for(Statement s: _mConsumableStatements)
      {
          System.out.println("s:"+s);
  
          Boolean isConflict=false;
          Resource uri=s.getSubject();
  
          System.out.println("uri:"+uri);
          System.out.println("1");
  
          if(RepStatementsAsHash.containsKey(uri))
          {
              System.out.println("2");
  
              if(RepStatementsAsHash.get(uri).containsKey(RDFS.LABEL))
                  RepStatementsAsHash.get(uri).remove(RDFS.LABEL);
              else if(RepStatementsAsHash.get(uri).containsKey(RDFS.SUBCLASSOF))
                  RepStatementsAsHash.get(uri).remove(RDFS.SUBCLASSOF);
              else if(RepStatementsAsHash.get(uri).containsKey(RDFS.RANGE))
                  RepStatementsAsHash.get(uri).remove(RDFS.RANGE);
              else if(RepStatementsAsHash.get(uri).containsKey(RDF.TYPE))
              {
                  System.out.println("2.1");
  
                  Value RepTypeObject=RepStatementsAsHash.get(uri).get(RDF.TYPE);
                  Value ConsumableTypeObject=CStatements.get(uri).get(RDF.TYPE);
  
                  if (RepTypeObject.stringValue().equals(OWL.CLASS) || RepTypeObject.stringValue().equals(RDFS.CLASS))
                  {
                      if(ConsumableTypeObject.stringValue().equals(OWL.DATATYPEPROPERTY) || ConsumableTypeObject.stringValue().equals(OWL.OBJECTPROPERTY) || ConsumableTypeObject.stringValue().equals(RDF.PROPERTY))
                      {
                          isConflict=true;
                          //_mConflictingStatements.add(s);
                      }
                      else
                      {
                          RepStatementsAsHash.get(uri).remove(RepTypeObject);
                      }
                  }
                  else if(RepTypeObject.stringValue().equals(OWL.DATATYPEPROPERTY) || ConsumableTypeObject.stringValue().equals(OWL.OBJECTPROPERTY) || RepTypeObject.stringValue().equals(RDF.PROPERTY))
                  {
                      if (ConsumableTypeObject.stringValue().equals(OWL.CLASS) || ConsumableTypeObject.stringValue().equals(RDFS.CLASS))
                      {
                          isConflict=true;
                          //_mConflictingStatements.add(s);
                      }
                      else
                      {
  
                      }
                  }
                  else
                  {
                      if( !(RepTypeObject.stringValue().equals(OWL.DATATYPEPROPERTY) || ConsumableTypeObject.stringValue().equals(OWL.OBJECTPROPERTY) || RepTypeObject.stringValue().equals(RDF.PROPERTY) || ConsumableTypeObject.stringValue().equals(OWL.CLASS) || ConsumableTypeObject.stringValue().equals(RDFS.CLASS))  )
                      {
                          if(RepTypeObject.stringValue()!=ConsumableTypeObject.stringValue())
                          {
                              isConflict=true;
                          }
  
                      }
                  }
                  System.out.println("2.2");
                  if(!isConflict)
                      {
                          addStatementsInRepository(uri.stringValue(),c_import);
                      }
              } // LABEL-TYPE 
          }
          else // No  URI Conflict
              addStatementsInRepository(uri.stringValue(),c_import);
  
          System.out.println("3");
      }
  </code></pre>
  
  <p>It is showing error something like :</p>
  
  <pre><code>11:13:24.405 ERROR - error while importing Sesame data:
  java.util.ConcurrentModificationException: null
      at java.util.ArrayList$Itr.checkForComodification(ArrayList.java:859) ~[na:1.7.0_71]
      at java.util.ArrayList$Itr.next(ArrayList.java:831) ~[na:1.7.0_71]
      at org.apache.marmotta.platform.core.services.importer.rdf.RDFImporterImpl.importData2(RDFImporterImpl.java:433) [ulysses-core-1.0-alpha-2.jar:1.0-alpha-2]
  </code></pre>
  
  <p>How to resolve it?</p>