title: Read xlsx file with POI (SXSSFWorkbook)
body: <p>I'm trying to do my first tests of reading large xlsx file with POI, but to do a simple test with a small file I fail to show the value of a cell.</p>
  
  <p>Someone can tell me what is my mistake. All the suggestions are welcome. Thanks.</p>
  
  <p><strong>Test.java:</strong></p>
  
  <pre><code>import java.io.File;
  import java.io.FileInputStream;
  
  import org.apache.poi.openxml4j.opc.OPCPackage;
  import org.apache.poi.ss.usermodel.Sheet;
  import org.apache.poi.xssf.streaming.SXSSFWorkbook;
  import org.apache.poi.xssf.usermodel.XSSFWorkbook;
  
  public class Test {
  
      public static void main(String[] args) throws Throwable {
          File file = new File("/tmp/test.xlsx");
          OPCPackage pkg = OPCPackage.open(new FileInputStream(file.getAbsolutePath()));
          XSSFWorkbook xssfwb = new XSSFWorkbook(pkg);
  
          SXSSFWorkbook wb = new SXSSFWorkbook(xssfwb, 100);
          Sheet sh = wb.getSheet("Hola");
  
          System.out.println("Name: "+sh.getSheetName()); // Line 19
          System.out.println("Val: "+sh.getRow(1).getCell(1).getStringCellValue()); // Line 20
      }
  }
  </code></pre>
  
  <p><strong>Result:</strong></p>
  
  <pre><code>Name: Hola
  Exception in thread "main" java.lang.NullPointerException
      at Test.main(Test.java:20)
  </code></pre>
  
  <p><strong>test.xlsx:</strong></p>
  
  <p><img src="https://i.stack.imgur.com/ItRWE.png" alt="enter image description here"></p>