output: #fixed code
                               @Test
  	// @Ignore
  	public void testWrite() {
  		List<ItemCollection> col = null;
  		// read default content
  		try {
  			col = XMLItemCollectionAdapter
  					.readCollectionFromInputStream(getClass().getResourceAsStream("/document-example.xml"));
  		} catch (JAXBException e) {
  			Assert.fail();
  		} catch (IOException e) {
  			Assert.fail();
  		}
  
  		// create JAXB object
  		DocumentCollection xmlCol = null;
  		try {
  			xmlCol = XMLItemCollectionAdapter.putDocuments(col);
  		} catch (Exception e1) {
  
  			e1.printStackTrace();
  			Assert.fail();
  		}
  
  		// now write back to file
  		File file = null;
  		try {
  
  			file = new File("src/test/resources/export-test.xml");
  			JAXBContext jaxbContext = JAXBContext.newInstance(DocumentCollection.class);
  			Marshaller jaxbMarshaller = jaxbContext.createMarshaller();
  
  			// output pretty printed
  			jaxbMarshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
  
  			jaxbMarshaller.marshal(xmlCol, file);
  			jaxbMarshaller.marshal(xmlCol, System.out);
  
  		} catch (JAXBException e) {
  			e.printStackTrace();
  			Assert.fail();
  		}
  		Assert.assertNotNull(file);
  	}
input: #vulnerable code 
                               @Test
  	// @Ignore
  	public void testWrite() {
  		List<ItemCollection> col = null;
  		// read default content
  		try {
  			col = XMLItemCollectionAdapter
  					.readCollectionFromInputStream(getClass().getResourceAsStream("/document-example.xml"));
  		} catch (JAXBException e) {
  			Assert.fail();
  		} catch (IOException e) {
  			Assert.fail();
  		}
  
  		// create JAXB object
  		DocumentCollection xmlCol = null;
  		try {
  			xmlCol = XMLItemCollectionAdapter.putCollection(col);
  		} catch (Exception e1) {
  
  			e1.printStackTrace();
  			Assert.fail();
  		}
  
  		// now write back to file
  		File file = null;
  		try {
  
  			file = new File("src/test/resources/export-test.xml");
  			JAXBContext jaxbContext = JAXBContext.newInstance(DocumentCollection.class);
  			Marshaller jaxbMarshaller = jaxbContext.createMarshaller();
  
  			// output pretty printed
  			jaxbMarshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
  
  			jaxbMarshaller.marshal(xmlCol, file);
  			jaxbMarshaller.marshal(xmlCol, System.out);
  
  		} catch (JAXBException e) {
  			e.printStackTrace();
  			Assert.fail();
  		}
  		Assert.assertNotNull(file);
  	} 
                              #location 18 
                              #vulnerability type NULL_DEREFERENCE